Del Valle Regional Park Weather
Park • San Francisco Bay Area
Del Valle Regional Park wraps around Lake Del Valle, a five-mile-long reservoir in the Diablo Range about 10 miles south of Livermore. Visitors reach it by Mines Road and Del Valle Road. The East Bay Regional Park District runs the 4,395-acre park, with swim beaches, a marina, a 150-site campground, and the eastern end of the 28-mile Ohlone Wilderness Trail. The lake itself is part of the State Water Project's South Bay Aqueduct. It is the Livermore Valley's main place to get out on the water.
Plan your week
10-Day Forecast
Hour by hour
Hourly Forecast
Current Conditions
Comfort Breakdown
Del Valle Regional Park weather today and through the year
It's 53°F at Del Valle Regional Park right now (feels like 48°F), with 8 mph wind and a comfort score of 76. Monday's forecast high at Del Valle Regional Park is 53°F, 10°F below the mid November normal of 63°F. The best window today is 8 AM to 11 AM, at about 57°F with a 10 mph wind (comfort 73).
July is the warmest month at Del Valle Regional Park, with an average high of 88°F. December is the coldest, with an average low of 39°F. January is the wettest month (3.2 in.), out of about 16.8 in. a year. By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Del Valle Regional Park are September, June, and October. The best hours are usually 9 AM to noon in September, 9 AM to noon in June, and 11 AM to 2 PM in October.
Lake Del Valle lies in the hills south of the Livermore Valley and shares its hot, dry summers, but it gets its breeze from a different direction. A 2017 study of the Livermore Valley wine region's local climates found the southern hills cooler than the valley floor. Marine air reaches them over the Sunol Grade and through the Vallecitos Valley rather than straight down I-580. That afternoon breeze across the open water is what sailboarders come for.
Forecast updated November 15, 2026 at 4:00 AM PST. Climate figures come from NOAA 1991-2020 normals. Hourly patterns come from NOAA's HRRR hourly analysis from September 2014 to April 2026.
What to expect at Del Valle Regional Park in the next few days
No active National Weather Service alerts for this location.
Best time to go
The best window today is 8 AM to 11 AM, at about 57°F with a 10 mph wind (comfort 73).
Hiking conditions
Best hiking day this week: Monday, with 9 daylight hours that are dry, 45 to 80°F, and under 18 mph wind. 5 of the next 7 days have at least 4 such hours.
Best day this week
Of the next 7 days, Friday looks best for Del Valle Regional Park, with a 59°F high and midday comfort near 74. Wednesday looks weakest (42).
Rain
Next good chance of rain: today (82%, about 0.05 in.).
Live weather map
Weather around Del Valle Regional Park right now
Overcast and 53° at Del Valle Regional Park right now.
About the live weather map for Del Valle Regional Park
The map centers on Del Valle Regional Park and stacks fog, satellite clouds, and precipitation radar on one view. Clouds come from the GOES-West satellite and rain from NOAA radar, and both show current conditions. Fog comes from our HRRR-based fog model, and the slider steps through its forecast for the next 12 hours.
Dots mark nearby places with their current temperature, colored by comfort score. Use the layer buttons to turn any layer off, or open the full map for every destination in the region.
Nearby Temperature Comparison
Conditions at nearby San Francisco Bay Area destinations
Tip: Bay Area temperatures can change by 20 to 30°F over a short distance because of microclimates.
Del Valle Regional Park vs nearby places
Typical summer conditions compared with Del Valle Regional Park, from the same NOAA HRRR hourly record. The list shows the closest places, then nearby places whose climate differs the most.
| Place | Distance | Summer afternoons | Morning fog | Afternoon wind | Compared with Del Valle Regional Park |
|---|---|---|---|---|---|
| Livermore | 8.1 mi | +2°F | 6% | 8 mph | a very similar climate |
| Sunol Regional Wilderness | 8.9 mi | -3°F | 10% | 10 mph | about 36% more rain a year |
| Pleasanton | 11.5 mi | +1°F | 4% | 6 mph | calmer summer afternoons (6 vs 11 mph) |
| Garin Regional Park | 18.9 mi | -10°F | 43% | 10 mph | more summer morning fog (43% vs 10% of morning hours) and about 10°F cooler on summer afternoons |
| Don Edwards Wildlife Refuge | 21.3 mi | -21°F | 18% | 16 mph | about 21°F cooler on summer afternoons and windier summer afternoons (16 vs 11 mph) |
| Coyote Hills Regional Park | 22.1 mi | -21°F | 21% | 14 mph | about 21°F cooler on summer afternoons and more summer morning fog (21% vs 10% of morning hours) |
Places with a climate like Del Valle Regional Park's
- Dublin (16 mi away): similar temperatures through the year
- Concord (33 mi away): similar temperatures through the year
- Pleasant Hill (32 mi away): similar temperatures through the year
Climate Dashboard
Current conditions vs. NOAA normals and recent destination baseline
What the Del Valle Regional Park climate comparisons mean
These cards compare recent conditions at Del Valle Regional Park with the available local baseline. Temperature and year-to-date rainfall use long-term normals when available. Fog, sunshine, wind, and comfort use the matching recent or modeled baseline identified on each card.
Positive and negative differences describe how Del Valle Regional Park departs from its own usual pattern. They should not be read as a direct comparison with another city or as a forecast beyond the period shown.
Del Valle Regional Park weather by month
July is the warmest month at Del Valle Regional Park, with an average high of 88°F. December is the coldest, with an average low of 39°F. January is the wettest month (3.2 in.), out of about 16.8 in. a year. Morning fog peaks in December, when fog or low cloud covers 19% of the hours from 6 to 10 AM. July has the clearest middays, with clouds covering about 2% of the sky from 11 AM to 3 PM.
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Del Valle Regional Park are September, June, and October. The best hours are usually 9 AM to noon in September, 9 AM to noon in June, and 11 AM to 2 PM in October.
| Month | Avg high | Avg low | Rain | Rainy days | Morning fog | Midday cloud | Afternoon wind | Daylight | Comfort |
|---|---|---|---|---|---|---|---|---|---|
| Jan | 56°F | 39°F | 3.2 in | 7 | 13% | 29% | 7 mph | 9.9 h | 58 |
| Feb | 58°F | 41°F | 3.1 in | 7 | 7% | 23% | 9 mph | 10.8 h | 61 |
| Mar | 63°F | 43°F | 2.5 in | 7 | 6% | 28% | 9 mph | 11.9 h | 65 |
| Apr | 67°F | 46°F | 1.3 in | 5 | 7% | 20% | 10 mph | 13.2 h | 75 |
| May | 74°F | 50°F | 0.6 in | 3 | 10% | 13% | 11 mph | 14.2 h | 81 |
| Jun | 82°F | 55°F | 0.1 in | 2 | 7% | 4% | 11 mph | 14.7 h | 87 |
| Jul | 88°F | 60°F | 0.0 in | 0 | 11% | 2% | 11 mph | 14.5 h | 83 |
| Aug | 88°F | 60°F | 0.0 in | 1 | 10% | 3% | 10 mph | 13.6 h | 83 |
| Sep | 84°F | 57°F | 0.1 in | 1 | 11% | 7% | 9 mph | 12.3 h | 88 |
| Oct | 75°F | 51°F | 0.8 in | 4 | 7% | 10% | 8 mph | 11.1 h | 85 |
| Nov | 63°F | 43°F | 1.8 in | 5 | 7% | 19% | 6 mph | 10.1 h | 76 |
| Dec | 55°F | 39°F | 3.1 in | 7 | 19% | 29% | 6 mph | 9.6 h | 56 |
Morning fog is the share of hours from 6 to 10 AM with fog or low cloud. Midday cloud is the average from 11 AM to 3 PM, and afternoon wind is the average from 1 to 5 PM. The highlighted rows are the most comfortable months.
What makes Del Valle Regional Park's weather different
Among the 58 San Francisco Bay Area parks we track, Del Valle Regional Park has the sunniest summer middays.
- #1of 58
sunniest summer middaysamong San Francisco Bay Area parks
When the fog burns off
noonwhen December fog usually thins (21% foggy at 8 AM)
Fog or low cloud covers Del Valle Regional Park in 21% of 8 AM hours in December, the foggiest month. It usually thins to a third of that by noon. March mornings are the least foggy (6%).
When the wind picks up
noonwhen afternoon wind builds, March–October
From March through October, wind at Del Valle Regional Park typically builds after noon. In May it peaks around 5 PM, averaging 12 mph with 16% of those hours windy, while mornings average 5 mph.
Hot hours
2 habove 85°F on a typical July afternoon
In July, the average temperature stays at or above 85°F for 2 hours a day.
Daylight
9.6–14.7 hof daylight, Dec to Jun
Days at Del Valle Regional Park range from about 9.6 hours in December to 14.7 hours in June. In mid-June the sun sets around 8:28 PM, and in mid-December around 4:55 PM.
Seasons at Del Valle Regional Park
- Warm seasonJun 25 – Sep 25 · highs 83°F+
The warm season lasts about 3.1 months, from Jun 25 to Sep 25, when the average high is 83°F or warmer. Highs peak around Jul 8 at about 88°F.
- Hot afternoonsJul 1 – Sep 4 · highs 85°F+
Average highs reach 85°F or more from Jul 1 to Sep 4.
- Cool seasonNov 29 – Feb 26 · highs 60°F or lower
The cool season runs from Nov 29 to Feb 26, when the average high is 60°F or lower. The coldest nights come around Dec 8, with an average low near 39°F.
- Rainy seasonNov 26 – Mar 22 · 69% of the year's rain
The rainy season runs from Nov 26 to Mar 22, when a day has at least a 20% chance of measurable rain. That stretch brings 69% of the year's rain.
The dark line marks today. Season dates come from the smoothed daily NOAA 1991-2020 normals. Counting from Oct. 1, a typical year has its first inch of rain by Nov 3 and half of its annual total by Jan 26.
Days per year and extremes (Nov 1, 2024 to Oct 31, 2026)
This record runs from Nov 1, 2024 to Oct 31, 2026. Over this record, Del Valle Regional Park averaged 27 days a year at 90°F or hotter and no freezing nights. It averaged 9 days a year with at least half an inch of rain and 3 afternoons with wind of 20 mph or more at 2 PM. About 56 mornings a year had 3 or more hours of fog or low cloud.
In the same record, the hottest day was Sep 9, 2026 (99°F) and the coldest night was Feb 20, 2026 (36°F). The wettest day was Oct 14, 2025 (1.58 in.), and the strongest 2 PM gust was 51 mph on Mar 12, 2025.
- 27days at 90°F or hotter
- 0nights at or below freezing
- 9days with ½ in. of rain or more
- 3afternoons with 20+ mph wind
- 56mornings with 3+ hours of fog or low cloud
- Hottest day99°FSep 9, 2026
- Coldest night36°FFeb 20, 2026
- Wettest day1.58 inOct 14, 2025
- Strongest 2 PM gust51 mphMar 12, 2025
What shapes Del Valle Regional Park's weather
The lake sits low, ringed by steeper hills. On clear, calm nights cold air drains down those slopes and settles over the water and the campground. Mornings can be much cooler than the afternoon heat suggests, and winter nights by the lake are cold.
Winter storms fill the lake and the creeks that feed it, and they can bring slides onto nearby roads. In 2023 the state water department cleared mudslide debris from roadways around the lake. The water level rises and falls through the year, which moves the shoreline and can leave a swim beach dry.
Long, hot summers warm the shallow edges of the lake, which favors blue-green algae, a bloom of bacteria that can make the water unsafe. The park district posts algae advisories when it is present.
Tips for visiting Del Valle Regional Park
Check the algae advisory before swimming
The park district posts current water-quality conditions for the East Swim Beach and has issued blue-green algae caution advisories for the lake.
Swim in the guarded zone
Swimming is allowed in designated areas south of the boat ramp, with lifeguards on duty as posted. North of the ramp there are no lifeguards.
Plan for boat quarantine
Golden mussels have been found in the lake, so a boat launched here is quarantined for 30 days from other park district waters. The speed limit on the lake is 10 mph.
Expect a flat fee on summer weekends
From April through Labor Day, weekends and holidays carry a flat entry fee that covers parking and boat launch.
Book campsites weeks ahead
Family sites can be reserved up to 12 weeks in advance. Campers with watercraft must pass boat inspection before checking in.
Carry water on the hill trails
Trails climb from the lake into open hills. The park district asks hikers to bring plenty of water and be ready for sudden weather changes.
Del Valle Regional Park through the seasons
- Spring (March–May)
- Spring brings green hills and the start of the bass season, with largemouth and smallmouth biting well through spring and summer.
- Summer (June–August)
- Summer is peak swimming and boating season, with gates open from 6 a.m. to 9 p.m. from May through Labor Day. Afternoons are hot, so check the algae advisory before getting in the water.
- Fall (September–November)
- Crowds thin after Labor Day, and the state stocks the lake with trout from October through May as the water cools.
- Winter (December–February)
- Winter is prime trout fishing season. Storms raise the lake and can bring slides onto the roads around it, so watch for debris on Mines Road and Del Valle Road.
Activities and the weather that matters
- Swimming: Hot, calm summer afternoons are ideal, as long as lifeguards are posted and no algae advisory is in effect.
- Sailboarding and windsurfing: They need the afternoon breeze that reaches these southern hills over the Sunol Grade and through the Vallecitos Valley. Still mornings suit paddling instead.
- Fishing: Trout fishing is best from fall through spring, when the lake is stocked. Bass bite in the warm months.
- Camping: Spring and fall are the most comfortable. Summer days are hot and nights by the lake can be chilly.
- Hiking the Ohlone Wilderness Trail: The trail heads into 28 miles of back country. Go on cool days in spring or after the first fall rains and avoid summer heat.
Official sources and current conditions
- East Bay Regional Park District: Del Valle
- East Bay Regional Park District: alerts and closures
- Del Valle map brochure (PDF)
Numbers on this page come from NOAA data. The text draws on the official sources linked above.
Historical Climate Data
Long-term weather patterns and climate data
Data sources: Recent temperatures come from NOAA URMA and recent precipitation from NOAA Stage IV. Fog, cloud, wind, humidity, and sunshine come from NOAA HRRR, and long-term baselines from NOAA 1991-2020 climate normals.
Climate Overview
Based on NOAA 30-year temperature/rain normals (1991-2020) with recent fog/sun baseline
🌟 Best Months to Visit
⚠️ Challenging Months
Monthly Breakdown
| Month | Comfort | High/Low | ☀️ Sun | 🌫️ Fog | 💧 Rain | Perfect |
|---|---|---|---|---|---|---|
| November 2024 | 83 | 61.5° / 47.6° | 6.5h | 0d | 1.46" | 21 |
| December 2024 | 75 | 59.9° / 47.1° | 5.1h | 4d | 3.09" | 13 |
| January 2025 | 83 | 58.1° / 43.2° | 7.2h | 2d | 0.16" | 24 |
| February 2025 | 80 | 59.8° / 46.4° | 6.9h | 1d | 3.76" | 17 |
| March 2025 | 83 | 59.8° / 45.5° | 8.4h | 0d | 2.57" | 20 |
| April 2025 | 92 | 66.3° / 47.6° | 10h | 1d | 0.47" | 27 |
| May 2025 | 94 | 74.6° / 51.4° | 12.3h | 1d | 0.05" | 30 |
| June 2025 | 96 | 79.6° / 53.1° | 12.7h | 1d | 0" | 30 |
| July 2025 | 93 | 80.9° / 55° | 12.3h | 5d | 0" | 31 |
| August 2025 | 91 | 85.6° / 59.6° | 11.4h | 4d | 0" | 31 |
| September 2025 | 92 | 81° / 60.5° | 10h | 3d | 0.12" | 29 |
| October 2025 | 90 | 71.4° / 54.3° | 8.1h | 4d | 2.19" | 28 |
| November 2025 | 81 | 64.1° / 50° | 6.5h | 8d | 2.54" | 19 |
| December 2025 | 76 | 57.9° / 44.6° | 5.7h | 13d | 1.6" | 10 |
| January 2026 | 82 | 59.6° / 47.7° | 6.9h | 1d | 1.89" | 22 |
| February 2026 | 81 | 61.8° / 48.5° | 6.8h | 5d | 3.7" | 19 |
| March 2026 | 96 | 74° / 56.1° | 9.9h | 1d | 0" | 30 |
| April 2026 | 89 | 66.3° / 49.3° | 9.5h | 0d | 2.38" | 26 |
| May 2026 | 92 | 73.4° / 52.1° | 11.5h | 4d | 0.19" | 30 |
| June 2026 | 93 | 80.7° / 55.2° | 12.3h | 1d | 0" | 30 |
| July 2026 | 92 | 83.7° / 57.8° | 12.2h | 1d | 0.04" | 31 |
| August 2026 | 91 | 85.5° / 58° | 11.3h | 3d | 0" | 31 |
| September 2026 | 93 | 79.2° / 56.8° | 10.4h | 4d | 0.03" | 29 |
| October 2026 | 89 | 77.3° / 57.5° | 8.4h | 1d | 0.17" | 26 |
Climate Trends
Average Temperature by Month
About the Del Valle Regional Park climate charts
The temperature chart compares average monthly highs and lows at Del Valle Regional Park, showing both the seasonal cycle and the typical day-to-night range. The comfort chart summarizes how often the combined weather pattern is favorable rather than judging temperature alone.
Precipitation shows the total recorded or modeled rainfall for each month at Del Valle Regional Park. Sunshine compares average bright-sky hours with the daylight available, while fog shows the average number of morning fog or low-cloud hours per day. Switch between the chart tabs to compare the same months across each measure.
Hourly Temperature, Fog, Wind, Cloud Cover, and Solar Radiation Patterns
Average local hour by month from 2014-09-30 to 2026-04-30
- Temperature: At Del Valle Regional Park, the warmest typical hour is 3 PM in July (86°F). The coldest is 7 AM in December (45°F).
- Fog: Fog or low cloud covers Del Valle Regional Park in 21% of 8 AM hours in December, the foggiest month. It usually thins to a third of that by noon. March mornings are the least foggy (6%).
- Wind: From March through October, wind at Del Valle Regional Park typically builds after noon. In May it peaks around 5 PM, averaging 12 mph with 16% of those hours windy, while mornings average 5 mph.
- Cloud Cover: July middays are the clearest at Del Valle Regional Park (2% average cloud cover), and January middays are the cloudiest (29%).
- Solar Radiation: The strongest typical sun at Del Valle Regional Park comes at 1 PM in June, averaging 1006 W/m².
How to read the hourly heatmaps for Del Valle Regional Park
This heatmap shows how average temperature at Del Valle Regional Park changes by hour and month. Read left to right for the seasons and top to bottom for the time of day. Warmer colors mark the usual afternoon peaks, and cooler colors show overnight and winter lows.
This heatmap shows when fog or low cloud is most likely at Del Valle Regional Park. Darker cells mark the months and hours when fog has been most common. They help separate overnight or morning fog from cloud that tends to linger into the afternoon.
This heatmap shows the typical hourly wind pattern at Del Valle Regional Park through the year. It makes recurring afternoon wind, calmer overnight periods, and seasonal changes easier to compare than a single daily wind value.
This heatmap shows average cloud cover at Del Valle Regional Park for every month and hour. Use it to see whether cloudiness is mainly an overnight and morning pattern or commonly persists during the part of the day you plan to visit.
This heatmap shows the average solar radiation reaching Del Valle Regional Park by month and hour. Brighter cells indicate the strongest typical sun, while muted cells can reflect nighttime, shorter winter days, cloud cover, smoke, or terrain shading.
Each cell combines one month with one local hour. Hover over or focus on a cell for its value and sample coverage. The red marker shows the current month and hour.
How recent months compared at Del Valle Regional Park
- October 2026 recap: October 2026 at Del Valle Regional Park averaged a high of 77°F, 6°F warmer than October 2025 (71°F).
- Rain year: The 2025-26 rain year (Oct. 1 to Sep. 30) brought 14.6 in. of rain to Del Valle Regional Park, 87% of the 16.8 in. normal.
Location Details
Del Valle Regional Park weather questions
Everything you need to know about weather and visiting Del Valle Regional Park
What is the weather like at Del Valle Regional Park today?
It's 53°F at Del Valle Regional Park right now, with a comfort score of 76 (great). Monday's forecast high at Del Valle Regional Park is 53°F, 10°F below the mid November normal of 63°F. The best window today is 8 AM to 11 AM, at about 57°F with a 10 mph wind (comfort 73).
What is the best month to visit Del Valle Regional Park?
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Del Valle Regional Park are September, June, and October. The best hours are usually 9 AM to noon in September, 9 AM to noon in June, and 11 AM to 2 PM in October. The warm season lasts about 3.1 months, from Jun 25 to Sep 25, when the average high is 83°F or warmer. Highs peak around Jul 8 at about 88°F.
What are the warmest and coldest months at Del Valle Regional Park?
July is the warmest month at Del Valle Regional Park, with an average high of 88°F. December is the coldest, with an average low of 39°F.
When does the fog burn off at Del Valle Regional Park?
Fog or low cloud covers Del Valle Regional Park in 21% of 8 AM hours in December, the foggiest month. It usually thins to a third of that by noon. March mornings are the least foggy (6%).
When is it windiest at Del Valle Regional Park?
From March through October, wind at Del Valle Regional Park typically builds after noon. In May it peaks around 5 PM, averaging 12 mph with 16% of those hours windy, while mornings average 5 mph.
How much rain does Del Valle Regional Park get?
January is the wettest month (3.2 in.), out of about 16.8 in. a year. The rainy season runs from Nov 26 to Mar 22, when a day has at least a 20% chance of measurable rain. That stretch brings 69% of the year's rain. The 2025-26 rain year (Oct. 1 to Sep. 30) brought 14.6 in. of rain to Del Valle Regional Park, 87% of the 16.8 in. normal.
Can you swim at Lake Del Valle?
Yes, in designated areas south of the boat ramp. North of the ramp swimming is allowed but no lifeguards are on duty, so you swim at your own risk. Check the park district's water-quality notice first, since blue-green algae advisories are posted for the lake. Low water has at times left the West Swim Beach dry.
What kind of place is Del Valle Regional Park?
Del Valle Regional Park wraps around Lake Del Valle, a five-mile-long reservoir in the Diablo Range about 10 miles south of Livermore. Visitors reach it by Mines Road and Del Valle Road. The East Bay Regional Park District runs the 4,395-acre park, with swim beaches, a marina, a 150-site campground, and the eastern end of the 28-mile Ohlone Wilderness Trail. The lake itself is part of the State Water Project's South Bay Aqueduct. It is the Livermore Valley's main place to get out on the water.
What is Del Valle Regional Park weather like in November?
November at Del Valle Regional Park averages a high of 63°F and a low of 43°F, with 1.8 in. of rain over about 5 rainy days. Afternoon wind averages 6 mph.
More about Del Valle Regional Park weather
Data sources and methods
- Monthly temperatures and precipitation: NOAA 1991-2020 normals.
- Fog, cloud, wind, sun, and comfort by hour and month: NOAA's HRRR hourly analysis from September 2014 to April 2026.
- Daily records and recent months: NOAA URMA and HRRR analyses, plus NOAA Stage IV precipitation.
- Nearby comparisons and regional rankings use the same hourly HRRR summaries for every destination in the region.
- Alerts: National Weather Service. Tides and ocean temperature: NOAA CO-OPS, where shown.
- All statements on this page are computed from these datasets, apart from the “What shapes the weather” guide, which cites its sources inline.
- East Bay Regional Park District, Del Valle Regional Park (accessed 2026-10-27)
- East Bay Regional Park District, Del Valle map brochure (2026) (accessed 2026-10-27)
- Patrick L. Shabram, Mesoclimate Patterns of the Livermore Valley AVA (2017, prepared for the Livermore Valley Winegrowers Association) (accessed 2026-10-27)
- California Department of Water Resources, Lake Del Valle and Del Valle Dam Mudslide Repairs (CEQA notice, 2023) (accessed 2026-10-27)
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