Foster City Weather
Town • San Francisco Bay Area
Foster City is a planned city on the bay side of Highway 101, built on what was Brewer's Island after developer T. Jack Foster took an option on the land in 1958. Neighborhoods wrap around a network of lagoons used for paddling, sailing, and swimming. A levee carrying the Bay Trail rings the city from the San Mateo-Hayward Bridge to Belmont Slough. No other town on this stretch of the Peninsula sits so completely out on the open bay, with no hills anywhere inside its limits.
Plan your week
10-Day Forecast
Hour by hour
Hourly Forecast
Current Conditions
Comfort Breakdown
Foster City weather today and through the year
It's 53°F at Foster City right now (feels like 49°F), with 7 mph wind and a comfort score of 76. Monday's forecast high at Foster City is 56°F, 8°F below the mid November normal of 64°F. No fog in the forecast for today at Foster City. In November, 15% of morning hours here are foggy on average. The best window today is 11 AM to 2 PM, at about 54°F with a 3 mph wind (comfort 60).
September is the warmest month at Foster City, with an average high of 73°F. December is the coldest, with an average low of 44°F. December is the wettest month (3.8 in.), out of about 19.0 in. a year. By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Foster City are September, August, and July. The best hours are usually 1 PM to 4 PM in September, 3 PM to 6 PM in August, and 4 PM to 7 PM in July.
Foster City is flat and surrounded by water, and the afternoon sea breeze reaches it with nothing in the way. Marine air entering the bay through the Golden Gate and the San Bruno Gap spreads south across open water through the afternoon. Foster City's shoreline takes it head on. Downtown San Mateo and Belmont, set back from the bay against the hills, run much warmer on summer afternoons.
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 Foster City in the next few days
No active National Weather Service alerts for this location.
Fog
No fog in the forecast for today at Foster City. In November, 15% of morning hours here are foggy on average.
Best time to go
The best window today is 11 AM to 2 PM, at about 54°F with a 3 mph wind (comfort 60).
Best day this week
Of the next 7 days, Friday looks best for Foster City, with a 61°F high and midday comfort near 79. Thursday looks weakest (51).
Rain
Next good chance of rain: today (77%, about 0.19 in.).
Live weather map
Weather around Foster City right now
Overcast and 53° at Foster City right now.
About the live weather map for Foster City
The map centers on Foster City 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.
Foster City vs nearby places
Typical summer conditions compared with Foster City, 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 Foster City |
|---|---|---|---|---|---|
| Belmont | 2.7 mi | +12°F | 13% | 12 mph | about 12°F warmer on summer afternoons |
| San Mateo | 3 mi | +12°F | 11% | 8 mph | about 12°F warmer on summer afternoons and calmer summer afternoons (8 vs 12 mph) |
| San Carlos | 3.6 mi | +13°F | 7% | 10 mph | about 13°F warmer on summer afternoons |
| Moss Beach | 13.4 mi | -5°F | 66% | 9 mph | more summer morning fog (66% vs 14% of morning hours) and about 47% more rain a year |
| Pleasanton | 22.9 mi | +22°F | 4% | 6 mph | about 22°F warmer on summer afternoons and calmer summer afternoons (6 vs 12 mph) |
| Danville | 23.5 mi | +21°F | 3% | 8 mph | about 21°F warmer on summer afternoons and calmer summer afternoons (8 vs 12 mph) |
Places with a climate like Foster City's
- Corte Madera (29 mi away): nearly the same temperatures every month
- San Rafael (32 mi away): similar temperatures through the year
- Ring Mountain Preserve (27 mi away): similar temperatures through the year
Climate Dashboard
Current conditions vs. NOAA normals and recent destination baseline
What the Foster City climate comparisons mean
These cards compare recent conditions at Foster City 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 Foster City 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.
Foster City weather by month
September is the warmest month at Foster City, with an average high of 73°F. December is the coldest, with an average low of 44°F. December is the wettest month (3.8 in.), out of about 19.0 in. a year. Morning fog peaks in December, when fog or low cloud covers 18% of the hours from 6 to 10 AM. June has the clearest middays, with clouds covering about 20% of the sky from 11 AM to 3 PM.
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Foster City are September, August, and July. The best hours are usually 1 PM to 4 PM in September, 3 PM to 6 PM in August, and 4 PM to 7 PM in July.
| Month | Avg high | Avg low | Rain | Rainy days | Morning fog | Midday cloud | Afternoon wind | Daylight | Comfort |
|---|---|---|---|---|---|---|---|---|---|
| Jan | 59°F | 44°F | 3.7 in | 8 | 17% | 35% | 6 mph | 9.9 h | 56 |
| Feb | 61°F | 46°F | 3.7 in | 8 | 15% | 27% | 9 mph | 10.8 h | 57 |
| Mar | 63°F | 48°F | 2.8 in | 7 | 11% | 30% | 10 mph | 11.9 h | 58 |
| Apr | 65°F | 49°F | 1.4 in | 5 | 8% | 25% | 11 mph | 13.2 h | 65 |
| May | 68°F | 52°F | 0.6 in | 3 | 8% | 29% | 12 mph | 14.2 h | 66 |
| Jun | 71°F | 54°F | 0.1 in | 2 | 13% | 20% | 12 mph | 14.7 h | 76 |
| Jul | 72°F | 56°F | 0.0 in | 0 | 16% | 23% | 12 mph | 14.5 h | 77 |
| Aug | 72°F | 57°F | 0.0 in | 1 | 14% | 24% | 12 mph | 13.6 h | 81 |
| Sep | 73°F | 56°F | 0.1 in | 1 | 16% | 23% | 11 mph | 12.3 h | 83 |
| Oct | 71°F | 53°F | 0.9 in | 4 | 16% | 21% | 9 mph | 11.1 h | 77 |
| Nov | 64°F | 48°F | 1.8 in | 6 | 15% | 23% | 7 mph | 10.1 h | 71 |
| Dec | 59°F | 44°F | 3.8 in | 8 | 18% | 35% | 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 Foster City's weather different
When the fog burns off
noonwhen December fog usually thins (21% foggy at 6 AM)
Fog or low cloud covers Foster City in 21% of 6 AM hours in December, the foggiest month. It usually thins to a third of that by noon. April mornings are the least foggy (8%).
When the wind picks up
1 PMwhen afternoon wind builds, February–November
From February through November, wind at Foster City typically builds after 1 PM. In May it peaks around 5 PM, averaging 13 mph with 27% of those hours windy, while mornings average 5 mph.
Microclimate
+13°FSan Carlos, 3.6 mi away, on summer afternoons
San Carlos, 3.6 miles away, runs about 13°F warmer than Foster City on summer afternoons.
Daylight
9.6–14.7 hof daylight, Dec to Jun
Days at Foster City range from about 9.6 hours in December to 14.7 hours in June. In mid-June the sun sets around 8:30 PM, and in mid-December around 4:57 PM.
Seasons at Foster City
- Warm seasonJun 8 – Oct 5 · highs 71°F+
The warm season lasts about 3.9 months, from Jun 8 to Oct 5, when the average high is 71°F or warmer. Highs peak around Sep 8 at about 73°F.
- Cool seasonNov 29 – Feb 28 · highs 62°F or lower
The cool season runs from Nov 29 to Feb 28, when the average high is 62°F or lower. The coldest nights come around Dec 8, with an average low near 44°F.
- Rainy seasonNov 20 – Mar 29 · 76% of the year's rain
The rainy season runs from Nov 20 to Mar 29, when a day has at least a 20% chance of measurable rain. That stretch brings 76% 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 2 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, Foster City averaged 10 days a year at 90°F or hotter and no freezing nights. It averaged 13 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 59 mornings a year had 3 or more hours of fog or low cloud.
In the same record, the hottest day was Sep 9, 2026 (98°F) and the coldest night was Jan 27, 2025 (37°F). The wettest day was Nov 23, 2024 (1.93 in.), and the strongest 2 PM gust was 42 mph on Mar 12, 2025.
- 10days at 90°F or hotter
- 0nights at or below freezing
- 13days with ½ in. of rain or more
- 3afternoons with 20+ mph wind
- 59mornings with 3+ hours of fog or low cloud
- Hottest day98°FSep 9, 2026
- Coldest night37°FJan 27, 2025
- Wettest day1.93 inNov 23, 2024
- Strongest 2 PM gust42 mphMar 12, 2025
What shapes Foster City's weather
Foster City's steady afternoon wind is why Baywinds Park is a kiteboarding base and the lagoon has a windsurfing school. The breeze usually builds from late morning, peaks in the mid to late afternoon in spring and summer, and eases around sunset. Mornings are typically calmer, which is when the lagoon is easiest for kayaks and paddleboards.
The bay and the lagoons take the edge off temperature extremes. The bay keeps summer afternoons milder than in inland Redwood City or Atherton, and winter nights a bit less cold than in the hill towns. The trade-off is exposure. The city sits barely above the bay, so its levee is its main defense against storm-driven high water.
Tips for visiting Foster City
Paddle the lagoon in the morning
The Leo Ryan Park boathouse rents kayaks, pedal boats, stand-up paddleboards, and windsurf boards. Go early, before the afternoon breeze builds.
Leave gas engines at home
Gas- and diesel-powered boats aren't allowed. Boats must run on sail, electric, or human power, with a 5 mph speed limit.
Swim with a buoy
Swimming is allowed throughout the lagoon. The city suggests daylight swims with high-visibility buoys or caps, and lends buoys free at the Leo Ryan Park boathouse.
Ride the levee loop
The city describes a 12-mile loop from Redwood Shores around the Bay Trail and back along Marina Lagoon, mostly on paved path.
Launch at Boat Park or Leo Ryan
The lagoon has two boat ramps, at Boat Park on Bounty Drive and Leo Ryan Park on Shell Boulevard. Small boats can launch anywhere.
Foster City through the seasons
- Spring (March–May)
- The windy season gets going, and kiteboard schools work out of Baywinds Park on breezy afternoons.
- Summer (June–August)
- The city raises the lagoon's water level in summer. Long, windy afternoons favor windsurfers over paddlers.
- Fall (September–October)
- Lighter winds and warm afternoons make this the easiest time for a paddle or a picnic at Leo Ryan Park.
- Winter (November–February)
- The city lowers the lagoon in winter so it can hold storm runoff. A federal flood study found most of the city's levee fell short of its standards, which led the city to start a major project to raise it.
Activities and the weather that matters
- Windsurfing and kiteboarding: Both sports need the afternoon sea breeze. Lessons run from the Leo Ryan Park boathouse and Baywinds Park.
- Kayaking and paddleboarding: Calm mornings are best. The lagoon sits inside the levee, away from bay waves, and averages about six feet deep.
- Walking and biking the levee: The levee path is flat and paved, but fully exposed. Expect a stiff headwind on one side of the loop on summer afternoons.
- Lagoon fishing: Non-commercial fishing is allowed, and the lagoon holds halibut and lots of baitfish. Calm mornings are easiest.
Official sources and current conditions
- Foster City: lagoon water activities
- Foster City: Leo J. Ryan Park
- Foster City: Levee Pedway
- Foster City: levee system
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 | 81 | 63.3° / 48.1° | 6.6h | 3d | 3.01" | 19 |
| December 2024 | 72 | 60.6° / 47° | 5h | 5d | 4.32" | 12 |
| January 2025 | 84 | 60.3° / 43.6° | 6.9h | 3d | 0.12" | 21 |
| February 2025 | 77 | 61.6° / 46.1° | 6.7h | 5d | 5.14" | 17 |
| March 2025 | 82 | 62.7° / 47.4° | 8.2h | 0d | 1.62" | 21 |
| April 2025 | 89 | 66.9° / 49.1° | 9.5h | 0d | 0.34" | 24 |
| May 2025 | 91 | 72.1° / 52.1° | 11.9h | 0d | 0.14" | 30 |
| June 2025 | 90 | 71.6° / 53.6° | 12.4h | 3d | 0" | 28 |
| July 2025 | 89 | 72.3° / 56.3° | 11.5h | 6d | 0" | 29 |
| August 2025 | 88 | 79° / 58.3° | 11h | 4d | 0" | 30 |
| September 2025 | 87 | 78.4° / 61° | 9.2h | 4d | 0.08" | 27 |
| October 2025 | 86 | 72.4° / 55.3° | 8h | 4d | 0.78" | 27 |
| November 2025 | 78 | 65.2° / 51.2° | 6.3h | 8d | 2.49" | 13 |
| December 2025 | 70 | 58.1° / 46.9° | 4.9h | 10d | 3.34" | 6 |
| January 2026 | 79 | 62° / 45.8° | 6.8h | 3d | 3.76" | 22 |
| February 2026 | 78 | 63.9° / 48.3° | 6.3h | 5d | 2.57" | 16 |
| March 2026 | 91 | 76.2° / 52.8° | 9.7h | 1d | 0.01" | 30 |
| April 2026 | 86 | 67.8° / 51.4° | 9h | 3d | 2.24" | 23 |
| May 2026 | 90 | 70.3° / 53.5° | 11.5h | 3d | 0.24" | 30 |
| June 2026 | 90 | 74.5° / 56.3° | 12.1h | 1d | 0" | 29 |
| July 2026 | 90 | 75.5° / 57.7° | 11.5h | 2d | 0" | 29 |
| August 2026 | 86 | 76.5° / 58.3° | 10.7h | 6d | 0" | 27 |
| September 2026 | 89 | 77.2° / 57.5° | 9.9h | 3d | 0.02" | 28 |
| October 2026 | 88 | 75.5° / 54.8° | 8.1h | 3d | 0.11" | 27 |
Climate Trends
Average Temperature by Month
About the Foster City climate charts
The temperature chart compares average monthly highs and lows at Foster City, 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 Foster City. 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 Foster City, the warmest typical hour is 5 PM in September (66°F). The coldest is 7 AM in January (50°F).
- Fog: Fog or low cloud covers Foster City in 21% of 6 AM hours in December, the foggiest month. It usually thins to a third of that by noon. April mornings are the least foggy (8%).
- Wind: From February through November, wind at Foster City typically builds after 1 PM. In May it peaks around 5 PM, averaging 13 mph with 27% of those hours windy, while mornings average 5 mph.
- Cloud Cover: June middays are the clearest at Foster City (20% average cloud cover), and December middays are the cloudiest (35%).
- Solar Radiation: The strongest typical sun at Foster City comes at 1 PM in July, averaging 968 W/m².
How to read the hourly heatmaps for Foster City
This heatmap shows how average temperature at Foster City 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 Foster City. 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 Foster City 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 Foster City 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 Foster City 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 Foster City
- October 2026 recap: October 2026 at Foster City averaged a high of 76°F, 5°F warmer than the 1991-2020 normal of 71°F. It brought 0.11 in. of rain, compared with a normal of 0.89 in.
- Rain year: The 2025-26 rain year (Oct. 1 to Sep. 30) brought 15.4 in. of rain to Foster City, 81% of the 19.0 in. normal.
Location Details
Foster City weather questions
Everything you need to know about weather and visiting Foster City
What is the weather like at Foster City today?
It's 53°F at Foster City right now, with a comfort score of 76 (great). Monday's forecast high at Foster City is 56°F, 8°F below the mid November normal of 64°F. The best window today is 11 AM to 2 PM, at about 54°F with a 3 mph wind (comfort 60).
What is the best month to visit Foster City?
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at Foster City are September, August, and July. The best hours are usually 1 PM to 4 PM in September, 3 PM to 6 PM in August, and 4 PM to 7 PM in July. The warm season lasts about 3.9 months, from Jun 8 to Oct 5, when the average high is 71°F or warmer. Highs peak around Sep 8 at about 73°F.
What are the warmest and coldest months at Foster City?
September is the warmest month at Foster City, with an average high of 73°F. December is the coldest, with an average low of 44°F.
When does the fog burn off at Foster City?
Fog or low cloud covers Foster City in 21% of 6 AM hours in December, the foggiest month. It usually thins to a third of that by noon. April mornings are the least foggy (8%).
When is it windiest at Foster City?
From February through November, wind at Foster City typically builds after 1 PM. In May it peaks around 5 PM, averaging 13 mph with 27% of those hours windy, while mornings average 5 mph.
How much rain does Foster City get?
December is the wettest month (3.8 in.), out of about 19.0 in. a year. The rainy season runs from Nov 20 to Mar 29, when a day has at least a 20% chance of measurable rain. That stretch brings 76% of the year's rain. The 2025-26 rain year (Oct. 1 to Sep. 30) brought 15.4 in. of rain to Foster City, 81% of the 19.0 in. normal.
How does Foster City weather compare with San Carlos?
San Carlos, 3.6 miles away, runs about 13°F warmer than Foster City on summer afternoons.
Can you swim in the Foster City lagoon?
Yes. The city allows swimming in all areas of the lagoon. It recommends swimming in daylight and using high-visibility buoys or caps, and it lends swim buoys free for short-term use at the Leo Ryan Park boathouse. Boats share the water, with a 5 mph speed limit.
What kind of place is Foster City?
Foster City is a planned city on the bay side of Highway 101, built on what was Brewer's Island after developer T. Jack Foster took an option on the land in 1958. Neighborhoods wrap around a network of lagoons used for paddling, sailing, and swimming. A levee carrying the Bay Trail rings the city from the San Mateo-Hayward Bridge to Belmont Slough. No other town on this stretch of the Peninsula sits so completely out on the open bay, with no hills anywhere inside its limits.
What is Foster City weather like in November?
November at Foster City averages a high of 64°F and a low of 48°F, with 1.8 in. of rain over about 6 rainy days. About 15% of morning hours are foggy. Afternoon wind averages 7 mph.
More about Foster City 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.
- City of Foster City, Water Activities (accessed 2026-10-27)
- City of Foster City, Levee Pedway (accessed 2026-10-27)
- City of Foster City, Levee System (accessed 2026-10-27)
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