St. Helena Weather
Town • San Francisco Bay Area
Highway 29 turns into Main Street in St. Helena, the historic upvalley town about 17 miles north of downtown Napa. Here Napa Valley pinches toward its narrowest point, with Spring Mountain rising on the west and Howell Mountain on the east. Vineyards run right up to the edge of town. Two state parks sit just north along the highway. Bale Grist Mill keeps its 1846 water-powered mill, and Bothe-Napa Valley protects redwood canyons.
Plan your week
10-Day Forecast
Hour by hour
Hourly Forecast
Current Conditions
Comfort Breakdown
St. Helena weather today and through the year
It's 52°F at St. Helena right now (feels like 49°F), with 5 mph wind and a comfort score of 76. Today's forecast high at St. Helena is 57°F, 9°F below the mid November normal of 66°F. No fog in the forecast for today at St. Helena. In November, 24% of morning hours here are foggy on average. The best window today is 8 AM to 11 AM, at about 53°F with a 3 mph wind (comfort 58).
July is the warmest month at St. Helena, with an average high of 89°F. December is the coldest, with an average low of 37°F. December is the wettest month (6.6 in.), out of about 31.8 in. a year. By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at St. Helena are September, October, and May. The best hours are usually 9 AM to noon in September, 10 AM to 1 PM in October, and 11 AM to 2 PM in May.
St. Helena runs hotter than Napa because the bay breeze has lost most of its cooling by the time it travels this far up the valley. Napa Valley Vintners say the valley floor here sees only occasional morning fog and call the area fairly hot, sometimes hotter than Calistoga. As the valley narrows, it also shelters the town from the wind and fog that reach Yountville and Oakville, and holds the heat in.
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 St. Helena in the next few days
No active National Weather Service alerts for this location.
Fog
No fog in the forecast for today at St. Helena. In November, 24% of morning hours here are foggy on average.
Best time to go
The best window today is 8 AM to 11 AM, at about 53°F with a 3 mph wind (comfort 58).
Best day this week
Of the next 7 days, Friday looks best for St. Helena, with a 59°F high and midday comfort near 72. Wednesday looks weakest (45).
Rain
Next good chance of rain: today (73%, about 0.31 in.).
Live weather map
Weather around St. Helena right now
Overcast and 52° at St. Helena right now.
About the live weather map for St. Helena
The map centers on St. Helena 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.
St. Helena vs nearby places
Typical summer conditions compared with St. Helena, 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 St. Helena |
|---|---|---|---|---|---|
| Rutherford | 4.1 mi | +1°F | 23% | 8 mph | a very similar climate |
| Angwin | 4.9 mi | -6°F | 14% | 10 mph | about 6°F cooler on summer afternoons and 1,364 ft higher |
| Sugarloaf Ridge State Park | 5 mi | -10°F | 17% | 10 mph | about 10°F cooler on summer afternoons and 1,338 ft higher |
| Cotati | 18 mi | -10°F | 31% | 10 mph | about 10°F cooler on summer afternoons |
| Sebastopol | 20.4 mi | -10°F | 30% | 10 mph | about 10°F cooler on summer afternoons and windier summer afternoons (10 vs 7 mph) |
| Olompali State Historic Park | 25 mi | -11°F | 35% | 9 mph | about 11°F cooler on summer afternoons and more summer morning fog (35% vs 24% of morning hours) |
Places with a climate like St. Helena's
- Napa (17 mi away): nearly the same temperatures every month
- Geyserville (27 mi away): similar temperatures through the year
- Cloverdale (36 mi away): similar temperatures through the year
Climate Dashboard
Current conditions vs. NOAA normals and recent destination baseline
What the St. Helena climate comparisons mean
These cards compare recent conditions at St. Helena 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 St. Helena 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.
St. Helena weather by month
July is the warmest month at St. Helena, with an average high of 89°F. December is the coldest, with an average low of 37°F. December is the wettest month (6.6 in.), out of about 31.8 in. a year. Morning fog peaks in December, when fog or low cloud covers 36% of the hours from 6 to 10 AM. July has the clearest middays, with clouds covering about 4% of the sky from 11 AM to 3 PM.
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at St. Helena are September, October, and May. The best hours are usually 9 AM to noon in September, 10 AM to 1 PM in October, and 11 AM to 2 PM in May.
| Month | Avg high | Avg low | Rain | Rainy days | Morning fog | Midday cloud | Afternoon wind | Daylight | Comfort |
|---|---|---|---|---|---|---|---|---|---|
| Jan | 58°F | 38°F | 6.5 in | 11 | 34% | 34% | 5 mph | 9.8 h | 42 |
| Feb | 62°F | 40°F | 6.3 in | 10 | 19% | 26% | 6 mph | 10.7 h | 50 |
| Mar | 67°F | 41°F | 4.5 in | 9 | 20% | 30% | 7 mph | 11.9 h | 69 |
| Apr | 71°F | 44°F | 1.9 in | 6 | 17% | 23% | 7 mph | 13.2 h | 79 |
| May | 78°F | 48°F | 1.0 in | 4 | 17% | 18% | 8 mph | 14.3 h | 82 |
| Jun | 85°F | 52°F | 0.2 in | 2 | 17% | 6% | 8 mph | 14.8 h | 78 |
| Jul | 89°F | 54°F | 0.0 in | 0 | 26% | 4% | 7 mph | 14.6 h | 76 |
| Aug | 89°F | 54°F | 0.0 in | 1 | 30% | 6% | 6 mph | 13.6 h | 78 |
| Sep | 87°F | 51°F | 0.1 in | 1 | 25% | 9% | 6 mph | 12.3 h | 83 |
| Oct | 79°F | 47°F | 1.5 in | 5 | 22% | 16% | 6 mph | 11.1 h | 83 |
| Nov | 66°F | 41°F | 3.2 in | 8 | 24% | 21% | 5 mph | 10.0 h | 71 |
| Dec | 57°F | 37°F | 6.6 in | 11 | 36% | 36% | 5 mph | 9.5 h | 38 |
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 St. Helena's weather different
When the fog burns off
noonwhen December fog usually thins (41% foggy at 5 AM)
Fog or low cloud covers St. Helena in 41% of 5 AM hours in December, the foggiest month. It usually thins to a third of that by noon. June mornings are the least foggy (17%).
When the wind picks up
3 PMwhen afternoon wind builds, April–September
From April through September, wind at St. Helena typically builds after 3 PM. In June it peaks around 5 PM, averaging 10 mph with 7% of those hours windy, while mornings average 5 mph.
Hot hours
6 habove 85°F on a typical July afternoon
In July, the average temperature stays at or above 85°F for 6 hours a day.
Elevation
−6°Fsummer afternoons at Angwin, 1,364 ft up
Angwin sits 1,364 ft higher, 4.9 miles away. Its summer highs average 6°F cooler and its winter lows 1°F milder than St. Helena.
Daylight
9.5–14.8 hof daylight, Dec to Jun
Days at St. Helena range from about 9.5 hours in December to 14.8 hours in June. In mid-June the sun sets around 8:34 PM, and in mid-December around 4:55 PM.
Seasons at St. Helena
- Warm seasonJun 26 – Sep 24 · highs 86°F+
The warm season lasts about 3 months, from Jun 26 to Sep 24, when the average high is 86°F or warmer. Highs peak around Jul 8 at about 89°F.
- Hot afternoonsJun 8 – Sep 26 · highs 85°F+
Average highs reach 85°F or more from Jun 8 to Sep 26.
- Cool seasonNov 27 – Feb 27 · highs 64°F or lower
The cool season runs from Nov 27 to Feb 27, when the average high is 64°F or lower. The coldest nights come around Dec 8, with an average low near 37°F.
- Rainy seasonOct 28 – Apr 12 · 88% of the year's rain
The rainy season runs from Oct 28 to Apr 12, when a day has at least a 20% chance of measurable rain. That stretch brings 88% 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 Oct 21 and half of its annual total by Jan 22.
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, St. Helena averaged 51 days a year at 90°F or hotter and 3 nights a year at or below freezing. It averaged 25 days a year with at least half an inch of rain and 0 afternoons with wind of 20 mph or more at 2 PM. About 115 mornings a year had 3 or more hours of fog or low cloud.
In the same record, the hottest day was Jun 11, 2026 (103°F) and the coldest night was Feb 18, 2026 (31°F). The wettest day was Nov 21, 2024 (6.28 in.), and the strongest 2 PM gust was 40 mph on Mar 12, 2025.
- 51days at 90°F or hotter
- 3nights at or below freezing
- 25days with ½ in. of rain or more
- 0afternoons with 20+ mph wind
- 115mornings with 3+ hours of fog or low cloud
- Hottest day103°FJun 11, 2026
- Coldest night31°FFeb 18, 2026
- Wettest day6.28 inNov 21, 2024
- Strongest 2 PM gust40 mphMar 12, 2025
What shapes St. Helena's weather
Late in the day, Spring Mountain and the Mayacamas Mountains shade the west side of St. Helena's valley floor first. The east side, under Howell Mountain, keeps the sun longer. After sunset, cooler air drains off both slopes onto the valley floor, so mornings stay fresh even after a hot afternoon.
Rain increases quickly as you head north and uphill. St. Helena gets noticeably more winter rain than Napa, and the forested canyons at Bothe-Napa Valley State Park just north of town get more still. The hills on both sides are also prime wildfire country in late summer and fall, when dry offshore winds blow from the interior toward the coast.
Tips for visiting St. Helena
Know your evacuation zone
The city maps its evacuation zones through Genasys Protect, including the Howell Mountain Road area, and recommends signing up for ALERT Napa County.
Head to the redwoods on hot days
Bothe-Napa Valley State Park, 5 miles north, has shaded redwood trails. State Parks says summer highs there can reach 105°F, with usually cool nights.
Check fire rules before grilling
Wood fires are periodically banned at Bothe. Charcoal can also be banned in high heat with low humidity or during Red Flag Warnings, the weather service's alerts for fire-spreading wind and dry air.
Get around with the St. Helena Shuttle
The on-demand shuttle picks riders up anywhere within the city. Book a ride by phone or through the Ride the Vine app.
Layer up for the Grist Mill
Bale Grist Mill, 3 miles north, is open weekends from 10 a.m. to 4 p.m. State Parks warns the weather there can be changeable.
St. Helena through the seasons
- Spring (March–May)
- Warm afternoons return while mornings stay cool. Late storms can still roll through in March and April, and the hillsides stay green into May.
- Summer (June–August)
- Summer days are hot and mostly sunny, with only occasional morning fog on the valley floor. Evenings cool off as air drains down from the hills.
- Fall (September–October)
- September stays nearly as hot as August while the harvest runs, and dry offshore wind raises fire danger. The 2020 Glass Fire started on September 27 off Crystal Springs Road, a few miles north of town.
- Winter (November–February)
- Winter is the rainy season, and the hillsides around town catch more of it than the valley floor. The city keeps sandbag stations at City Hall and Crane Park throughout the rainy season.
Activities and the weather that matters
- Strolling and shopping Main Street: Mornings and early evenings are best in summer. Midafternoon heat on the valley floor makes shaded sidewalks and indoor stops welcome.
- Hiking at Bothe-Napa Valley State Park: Redwood shade along Ritchey Canyon makes it the best hot-day hike near town. Most of the park's rain falls from December through March, so expect mud then.
- Cycling the Vine Trail to Calistoga: The section from St. Helena to Calistoga passes Bothe-Napa Valley State Park and makes a good morning ride. Start early in summer before the valley heats up.
- Touring Bale Grist Mill: The mill makes a good weekend outing in any season. Bring layers, since weather at the mill can change during a visit.
Official sources and current conditions
- City of St. Helena: emergency preparedness
- California State Parks: Bothe-Napa Valley State Park
- California State Parks: Bale Grist Mill State Historic Park
- VINE Transit: St. Helena Shuttle
- VINE Transit Route 10 (Up Valley Connector)
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 | 77 | 63.5° / 43.6° | 6h | 6d | 15.99" | 17 |
| December 2024 | 70 | 61.1° / 43.3° | 4.8h | 12d | 10.72" | 13 |
| January 2025 | 83 | 61.6° / 40.3° | 7.2h | 8d | 0.44" | 22 |
| February 2025 | 75 | 61.9° / 42.3° | 6.2h | 6d | 14.69" | 14 |
| March 2025 | 82 | 63.2° / 43.3° | 7.9h | 5d | 5.09" | 18 |
| April 2025 | 90 | 71° / 46.8° | 9.6h | 7d | 0.83" | 26 |
| May 2025 | 93 | 80.7° / 50.7° | 12.3h | 1d | 0.18" | 30 |
| June 2025 | 91 | 84.2° / 51.2° | 12.1h | 1d | 0" | 30 |
| July 2025 | 93 | 85° / 53.9° | 12.1h | 1d | 0" | 31 |
| August 2025 | 87 | 91.1° / 55.3° | 11.3h | 3d | 0" | 26 |
| September 2025 | 87 | 84.8° / 57° | 9.4h | 4d | 0.32" | 25 |
| October 2025 | 85 | 74.4° / 51.8° | 7.4h | 8d | 1.59" | 25 |
| November 2025 | 79 | 65.3° / 48.2° | 6.4h | 9d | 4.85" | 16 |
| December 2025 | 65 | 57.1° / 43.3° | 4.7h | 21d | 9.21" | 5 |
| January 2026 | 80 | 63.4° / 42.7° | 6.5h | 7d | 6.34" | 21 |
| February 2026 | 78 | 64.6° / 44.8° | 6.2h | 8d | 5.97" | 16 |
| March 2026 | 93 | 79.8° / 50° | 9.9h | 2d | 0" | 31 |
| April 2026 | 86 | 69.8° / 47.2° | 9.1h | 5d | 5.02" | 22 |
| May 2026 | 92 | 77.6° / 52.3° | 11.4h | 5d | 1.11" | 29 |
| June 2026 | 91 | 85.1° / 54.8° | 12.4h | 0d | 0" | 28 |
| July 2026 | 90 | 88.8° / 55.4° | 11.9h | 1d | 0" | 30 |
| August 2026 | 88 | 88.8° / 55.3° | 11h | 9d | 0" | 29 |
| September 2026 | 88 | 83.8° / 53.4° | 9.9h | 10d | 0.37" | 27 |
| October 2026 | 85 | 81.8° / 48.7° | 8.2h | 4d | 0.09" | 22 |
Climate Trends
Average Temperature by Month
About the St. Helena climate charts
The temperature chart compares average monthly highs and lows at St. Helena, 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 St. Helena. 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 St. Helena, the warmest typical hour is 4 PM in July (92°F). The coldest is 7 AM in December (45°F).
- Fog: Fog or low cloud covers St. Helena in 41% of 5 AM hours in December, the foggiest month. It usually thins to a third of that by noon. June mornings are the least foggy (17%).
- Wind: From April through September, wind at St. Helena typically builds after 3 PM. In June it peaks around 5 PM, averaging 10 mph with 7% of those hours windy, while mornings average 5 mph.
- Cloud Cover: July middays are the clearest at St. Helena (4% average cloud cover), and December middays are the cloudiest (36%).
- Solar Radiation: The strongest typical sun at St. Helena comes at 1 PM in June, averaging 986 W/m².
How to read the hourly heatmaps for St. Helena
This heatmap shows how average temperature at St. Helena 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 St. Helena. 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 St. Helena 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 St. Helena 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 St. Helena 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 St. Helena
- October 2026 recap: October 2026 at St. Helena averaged a high of 82°F, 7°F warmer than October 2025 (74°F).
- Rain year: The 2025-26 rain year (Oct. 1 to Sep. 30) brought 34.5 in. of rain to St. Helena, 108% of the 31.8 in. normal.
Location Details
St. Helena weather questions
Everything you need to know about weather and visiting St. Helena
What is the weather like at St. Helena today?
It's 52°F at St. Helena right now, with a comfort score of 76 (great). Today's forecast high at St. Helena is 57°F, 9°F below the mid November normal of 66°F. The best window today is 8 AM to 11 AM, at about 53°F with a 3 mph wind (comfort 58).
What is the best month to visit St. Helena?
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at St. Helena are September, October, and May. The best hours are usually 9 AM to noon in September, 10 AM to 1 PM in October, and 11 AM to 2 PM in May. The warm season lasts about 3 months, from Jun 26 to Sep 24, when the average high is 86°F or warmer. Highs peak around Jul 8 at about 89°F.
What are the warmest and coldest months at St. Helena?
July is the warmest month at St. Helena, with an average high of 89°F. December is the coldest, with an average low of 37°F.
When does the fog burn off at St. Helena?
Fog or low cloud covers St. Helena in 41% of 5 AM hours in December, the foggiest month. It usually thins to a third of that by noon. June mornings are the least foggy (17%).
When is it windiest at St. Helena?
From April through September, wind at St. Helena typically builds after 3 PM. In June it peaks around 5 PM, averaging 10 mph with 7% of those hours windy, while mornings average 5 mph.
How much rain does St. Helena get?
December is the wettest month (6.6 in.), out of about 31.8 in. a year. The rainy season runs from Oct 28 to Apr 12, when a day has at least a 20% chance of measurable rain. That stretch brings 88% of the year's rain. The 2025-26 rain year (Oct. 1 to Sep. 30) brought 34.5 in. of rain to St. Helena, 108% of the 31.8 in. normal.
How does St. Helena weather compare with Angwin?
Angwin sits 1,364 ft higher, 4.9 miles away. Its summer highs average 6°F cooler and its winter lows 1°F milder than St. Helena.
What kind of place is St. Helena?
Highway 29 turns into Main Street in St. Helena, the historic upvalley town about 17 miles north of downtown Napa. Here Napa Valley pinches toward its narrowest point, with Spring Mountain rising on the west and Howell Mountain on the east. Vineyards run right up to the edge of town. Two state parks sit just north along the highway. Bale Grist Mill keeps its 1846 water-powered mill, and Bothe-Napa Valley protects redwood canyons.
What is St. Helena weather like in November?
November at St. Helena averages a high of 66°F and a low of 41°F, with 3.2 in. of rain over about 8 rainy days. About 24% of morning hours are foggy. Afternoon wind averages 5 mph.
More about St. Helena weather
Guides that explain the weather here and nearby
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.
- Napa Valley Vintners, St. Helena AVA (accessed 2026-10-27)
- City of St. Helena, Emergency Preparedness (accessed 2026-10-27)
- California State Parks, Bothe-Napa Valley State Park (accessed 2026-10-27)
- California State Parks, Bale Grist Mill State Historic Park (accessed 2026-10-27)
- VINE Transit, St. Helena Shuttle (accessed 2026-10-27)
- CAL FIRE, Glass Fire incident (2020) (accessed 2026-10-27)
- Napa Valley Vine Trail Coalition, The Vine Trail (accessed 2026-10-27)
Rendered 2026-11-15T12:16:25.160Z.