South San Francisco Weather
Town • San Francisco Bay Area
South San Francisco fills a broad valley that opens east to the bay. San Bruno Mountain rises on its north side, and the Coast Range ridges stand to the west. The giant concrete letters on Sign Hill still spell out "South San Francisco The Industrial City" above downtown. The flats east of Highway 101 are better known today for biotech campuses and the Oyster Point waterfront, where a commuter ferry crosses to Oakland and Alameda.
Plan your week
10-Day Forecast
Hour by hour
Hourly Forecast
Current Conditions
Comfort Breakdown
South San Francisco weather today and through the year
It's 53°F at South San Francisco right now (feels like 51°F), with 4 mph wind and a comfort score of 77. Monday's forecast high at South San Francisco is 57°F, 6°F below the mid November normal of 63°F. The best window today is 8 AM to 11 AM, at about 54°F with a 7 mph wind (comfort 57).
September is the warmest month at South San Francisco, with an average high of 71°F. January is the coldest, with an average low of 45°F. December is the wettest month (4.8 in.), out of about 23.1 in. a year. By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at South San Francisco are September, August, and October. The best hours are usually 11 AM to 2 PM in September, 11 AM to 2 PM in August, and noon to 3 PM in October.
South City sits at the bay end of the San Bruno Gap. The gap is the low break in the Peninsula hills that runs from the Pacifica and Daly City coast toward the airport. On summer afternoons, when the Central Valley heats up, ocean air pours through that gap and fans out across the valley floor. That makes South San Francisco one of the windiest and grayest bayside cities on the Peninsula, even though it sits miles from the ocean.
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 South San Francisco 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 54°F with a 7 mph wind (comfort 57).
Best day this week
Of the next 7 days, Friday looks best for South San Francisco, with a 61°F high and midday comfort near 80. Thursday looks weakest (47).
Rain
Next good chance of rain: today (74%, about 0.33 in.).
Live weather map
Weather around South San Francisco right now
Overcast and 53° at South San Francisco right now.
About the live weather map for South San Francisco
The map centers on South San Francisco 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.
South San Francisco vs nearby places
Typical summer conditions compared with South San Francisco, 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 South San Francisco |
|---|---|---|---|---|---|
| San Bruno | 1.7 mi | +3°F | 15% | 11 mph | a very similar climate |
| Millbrae | 4 mi | +4°F | 13% | 10 mph | about 4°F warmer on summer afternoons and calmer summer afternoons (10 vs 13 mph) |
| Visitacion Valley | 4.2 mi | +1°F | 21% | 12 mph | a very similar climate |
| Montara | 9.8 mi | -12°F | 60% | 8 mph | more summer morning fog (60% vs 20% of morning hours) and about 12°F cooler on summer afternoons |
| Moss Beach | 10.5 mi | -10°F | 66% | 9 mph | more summer morning fog (66% vs 20% of morning hours) and about 10°F cooler on summer afternoons |
| Half Moon Bay | 13.3 mi | -6°F | 64% | 8 mph | more summer morning fog (64% vs 20% of morning hours) and calmer summer afternoons (8 vs 13 mph) |
Places with a climate like South San Francisco's
- Sausalito (15 mi away): nearly the same temperatures every month
- Ring Mountain Preserve (18 mi away): nearly the same temperatures every month
- Larkspur (21 mi away): nearly the same temperatures every month
Climate Dashboard
Current conditions vs. NOAA normals and recent destination baseline
What the South San Francisco climate comparisons mean
These cards compare recent conditions at South San Francisco 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 South San Francisco 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.
South San Francisco weather by month
September is the warmest month at South San Francisco, with an average high of 71°F. January is the coldest, with an average low of 45°F. December is the wettest month (4.8 in.), out of about 23.1 in. a year. Morning fog peaks in July, when fog or low cloud covers 23% of the hours from 6 to 10 AM. October has the clearest middays, with clouds covering about 24% of the sky from 11 AM to 3 PM.
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at South San Francisco are September, August, and October. The best hours are usually 11 AM to 2 PM in September, 11 AM to 2 PM in August, and noon to 3 PM in October.
| Month | Avg high | Avg low | Rain | Rainy days | Morning fog | Midday cloud | Afternoon wind | Daylight | Comfort |
|---|---|---|---|---|---|---|---|---|---|
| Jan | 58°F | 45°F | 4.5 in | 9 | 13% | 36% | 5 mph | 9.8 h | 58 |
| Feb | 60°F | 46°F | 4.5 in | 9 | 10% | 29% | 8 mph | 10.7 h | 60 |
| Mar | 62°F | 48°F | 3.3 in | 7 | 9% | 33% | 9 mph | 11.9 h | 63 |
| Apr | 64°F | 49°F | 1.6 in | 5 | 9% | 29% | 11 mph | 13.2 h | 68 |
| May | 66°F | 51°F | 0.7 in | 3 | 11% | 34% | 13 mph | 14.2 h | 68 |
| Jun | 68°F | 53°F | 0.2 in | 2 | 18% | 27% | 14 mph | 14.8 h | 78 |
| Jul | 69°F | 55°F | 0.0 in | 1 | 23% | 32% | 13 mph | 14.5 h | 80 |
| Aug | 70°F | 56°F | 0.1 in | 1 | 21% | 30% | 13 mph | 13.6 h | 85 |
| Sep | 71°F | 55°F | 0.1 in | 1 | 15% | 28% | 11 mph | 12.3 h | 88 |
| Oct | 69°F | 53°F | 1.1 in | 4 | 10% | 24% | 8 mph | 11.1 h | 84 |
| Nov | 63°F | 49°F | 2.4 in | 6 | 10% | 25% | 6 mph | 10.1 h | 68 |
| Dec | 58°F | 45°F | 4.8 in | 9 | 19% | 37% | 5 mph | 9.6 h | 57 |
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 South San Francisco's weather different
Among the 163 San Francisco Bay Area towns we track, South San Francisco has the 3rd-mildest winter nights.
- #3of 163
mildest winter nightsamong San Francisco Bay Area towns
When the fog burns off
25%of 8 AM hours foggy in July
Fog or low cloud covers South San Francisco in 25% of 8 AM hours in July, the foggiest month. It thins slowly and often lasts into the early afternoon. April mornings are the least foggy (9%).
When the wind picks up
2 PMwhen afternoon wind builds, February–October
From February through October, wind at South San Francisco typically builds after 2 PM. In June it peaks around 5 PM, averaging 15 mph with 47% of those hours windy, while mornings average 6 mph.
Microclimate
−12°FMontara, 9.8 mi away, on summer afternoons
Montara, 9.8 miles away, runs about 12°F cooler than South San Francisco on summer afternoons. It also has far more summer morning fog, 60% of morning hours compared with 20%.
Daylight
9.6–14.8 hof daylight, Dec to Jun
Days at South San Francisco range from about 9.6 hours in December to 14.8 hours in June. In mid-June the sun sets around 8:34 PM, and in mid-December around 4:58 PM.
Seasons at South San Francisco
- Warm seasonJul 8 – Oct 24 · highs 69°F+
The warm season lasts about 3.6 months, from Jul 8 to Oct 24, when the average high is 69°F or warmer. Highs peak around Sep 8 at about 71°F.
- Cool seasonNov 29 – Feb 28 · highs 61°F or lower
The cool season runs from Nov 29 to Feb 28, when the average high is 61°F or lower. The coldest nights come around Jan 8, with an average low near 45°F.
- Rainy seasonNov 12 – Apr 5 · 81% of the year's rain
The rainy season runs from Nov 12 to Apr 5, when a day has at least a 20% chance of measurable rain. That stretch brings 81% 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 30 and half of its annual total by Jan 24.
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, South San Francisco averaged 3 days a year at 90°F or hotter and no freezing nights. It averaged 15 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 73 mornings a year had 3 or more hours of fog or low cloud.
In the same record, the hottest day was Sep 9, 2026 (97°F) and the coldest night was Feb 20, 2026 (40°F). The wettest day was Nov 23, 2024 (2.74 in.), and the strongest 2 PM gust was 48 mph on Mar 12, 2025.
- 3days at 90°F or hotter
- 0nights at or below freezing
- 15days with ½ in. of rain or more
- 3afternoons with 20+ mph wind
- 73mornings with 3+ hours of fog or low cloud
- Hottest day97°FSep 9, 2026
- Coldest night40°FFeb 20, 2026
- Wettest day2.74 inNov 23, 2024
- Strongest 2 PM gust48 mphMar 12, 2025
What shapes South San Francisco's weather
Within South San Francisco, elevation matters. The neighborhoods that climb toward Sign Hill and San Bruno Mountain sit closer to the base of the marine layer, the low deck of cool, foggy ocean air. They can stay in cloud after the bayfront flats near Oyster Point have brightened. Even so, the overcast is usually thinner and more broken here than in Pacifica, a few miles west on the ocean side of the ridges.
The gap breeze is strongest on late spring and summer afternoons. It runs west to east across the valley floor and out over the business parks east of Highway 101. Mornings are typically calmer. Compared with Burlingame and San Mateo, which sit south of the gap behind higher hills, South City is cooler and breezier on most summer days.
Fall offshore patterns can bring South City its warmest days, when the gap flow reverses or stalls. Winter storms arrive from the southwest, and the hills around town, especially San Bruno Mountain, wring out more rain than the bay shoreline.
Tips for visiting South San Francisco
Dress for wind on Sign Hill
Weather on Sign Hill can differ greatly from the streets below, so bring a windproof layer even when downtown is mild.
Take the Letters Trail for shade
It is Sign Hill's only trail with views of the historic hillside sign, and it passes through a native oak grove with some shade.
Bring the dog to Sign Hill
Leashed dogs are welcome on Sign Hill's trails. City rules cap leashes at six feet.
Use the shuttle from BART
The city's South City Shuttle connects the South San Francisco BART station with points around town.
Plan a ferry trip for a weekday
The Oyster Point ferry is a weekday commute service to Oakland's Jack London Square and Main Street Alameda.
South San Francisco through the seasons
- Spring (March–May)
- Spring turns the hills green, and the gap breeze ramps up toward its June peak. Sign Hill is habitat for the endangered mission blue butterfly.
- Summer (June–August)
- Summer brings gray mornings, breezy afternoons, and fog often pouring through the gap by evening. Expect cooler days than in cities farther down the Peninsula.
- Fall (September–October)
- Fall is usually the warmest part of the year, when the sea breeze weakens. It is the best time for a clear view from Sign Hill.
- Winter (November–February)
- Winter is the rainy season, with gusty southerly winds ahead of storms. Clear days between systems bring the crispest views across the bay.
Activities and the weather that matters
- Hiking Sign Hill: The city lists nearly two miles of steep trails with bay views. Clear, calm mornings are best, and summer afternoons are windy and cool.
- Walking the Oyster Point shoreline: The shoreline is bright but often breezy. Go in the morning before the afternoon wind picks up off the bay.
- Ferry to the East Bay: The ferry runs weekday commute trips only. Morning crossings are usually smoother than the windy late-afternoon return.
Official sources and current conditions
- City of South San Francisco: Sign Hill
- BART: South San Francisco station
- SF Bay Ferry: South San Francisco route
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 | 62.4° / 49.4° | 6.6h | 3d | 4.31" | 22 |
| December 2024 | 72 | 60.1° / 48.3° | 5.2h | 10d | 5.26" | 12 |
| January 2025 | 84 | 59.9° / 45.6° | 6.8h | 1d | 0.16" | 21 |
| February 2025 | 75 | 60.6° / 46.6° | 6.6h | 6d | 6.14" | 13 |
| March 2025 | 82 | 61.3° / 47.6° | 8.3h | 1d | 1.78" | 20 |
| April 2025 | 88 | 63.2° / 48.9° | 9.5h | 0d | 0.36" | 24 |
| May 2025 | 90 | 66.5° / 51.3° | 11.8h | 2d | 0.14" | 29 |
| June 2025 | 86 | 65.2° / 52.5° | 12h | 8d | 0" | 24 |
| July 2025 | 88 | 66.3° / 55° | 10.8h | 7d | 0" | 26 |
| August 2025 | 89 | 70.6° / 57.1° | 10.6h | 6d | 0.07" | 28 |
| September 2025 | 91 | 73.5° / 59.8° | 9.5h | 1d | 0.12" | 29 |
| October 2025 | 88 | 69.8° / 55.5° | 7.8h | 2d | 1.05" | 26 |
| November 2025 | 79 | 63.6° / 52° | 6.6h | 6d | 3.45" | 15 |
| December 2025 | 70 | 57.2° / 47.5° | 5h | 13d | 4.06" | 7 |
| January 2026 | 79 | 61.2° / 47.8° | 6.6h | 3d | 4.76" | 20 |
| February 2026 | 78 | 63.2° / 49.4° | 6.5h | 4d | 3.97" | 18 |
| March 2026 | 93 | 73.1° / 53.3° | 9.6h | 1d | 0.02" | 29 |
| April 2026 | 85 | 65° / 51.8° | 9.1h | 3d | 3.64" | 23 |
| May 2026 | 88 | 65.8° / 52.6° | 11.2h | 6d | 0.51" | 24 |
| June 2026 | 91 | 68.9° / 54.9° | 11.9h | 2d | 0" | 29 |
| July 2026 | 89 | 68.7° / 56.3° | 11.1h | 8d | 0" | 27 |
| August 2026 | 89 | 69.3° / 56.8° | 10.5h | 9d | 0" | 28 |
| September 2026 | 91 | 71.3° / 57.1° | 9.7h | 3d | 0.05" | 28 |
| October 2026 | 91 | 72° / 55.1° | 8.4h | 2d | 0.15" | 30 |
Climate Trends
Average Temperature by Month
About the South San Francisco climate charts
The temperature chart compares average monthly highs and lows at South San Francisco, 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 South San Francisco. 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 South San Francisco, the warmest typical hour is 2 PM in September (73°F). The coldest is 7 AM in January (47°F).
- Fog: Fog or low cloud covers South San Francisco in 25% of 8 AM hours in July, the foggiest month. It thins slowly and often lasts into the early afternoon. April mornings are the least foggy (9%).
- Wind: From February through October, wind at South San Francisco typically builds after 2 PM. In June it peaks around 5 PM, averaging 15 mph with 47% of those hours windy, while mornings average 6 mph.
- Cloud Cover: October middays are the clearest at South San Francisco (24% average cloud cover), and December middays are the cloudiest (37%).
- Solar Radiation: The strongest typical sun at South San Francisco comes at 1 PM in June, averaging 907 W/m².
How to read the hourly heatmaps for South San Francisco
This heatmap shows how average temperature at South San Francisco 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 South San Francisco. 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 South San Francisco 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 South San Francisco 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 South San Francisco 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 South San Francisco
- October 2026 recap: October 2026 at South San Francisco averaged a high of 72°F, 3°F warmer than the 1991-2020 normal of 69°F. It brought 0.15 in. of rain, compared with a normal of 1.06 in.
- Rain year: The 2025-26 rain year (Oct. 1 to Sep. 30) brought 21.5 in. of rain to South San Francisco, 93% of the 23.1 in. normal.
Location Details
South San Francisco weather questions
Everything you need to know about weather and visiting South San Francisco
What is the weather like at South San Francisco today?
It's 53°F at South San Francisco right now, with a comfort score of 77 (great). Monday's forecast high at South San Francisco is 57°F, 6°F below the mid November normal of 63°F. The best window today is 8 AM to 11 AM, at about 54°F with a 7 mph wind (comfort 57).
What is the best month to visit South San Francisco?
By typical temperature, wind, cloud, humidity, and rain odds, the most comfortable months at South San Francisco are September, August, and October. The best hours are usually 11 AM to 2 PM in September, 11 AM to 2 PM in August, and noon to 3 PM in October. The warm season lasts about 3.6 months, from Jul 8 to Oct 24, when the average high is 69°F or warmer. Highs peak around Sep 8 at about 71°F.
What are the warmest and coldest months at South San Francisco?
September is the warmest month at South San Francisco, with an average high of 71°F. January is the coldest, with an average low of 45°F.
When does the fog burn off at South San Francisco?
Fog or low cloud covers South San Francisco in 25% of 8 AM hours in July, the foggiest month. It thins slowly and often lasts into the early afternoon. April mornings are the least foggy (9%).
When is it windiest at South San Francisco?
From February through October, wind at South San Francisco typically builds after 2 PM. In June it peaks around 5 PM, averaging 15 mph with 47% of those hours windy, while mornings average 6 mph.
How much rain does South San Francisco get?
December is the wettest month (4.8 in.), out of about 23.1 in. a year. The rainy season runs from Nov 12 to Apr 5, when a day has at least a 20% chance of measurable rain. That stretch brings 81% of the year's rain. The 2025-26 rain year (Oct. 1 to Sep. 30) brought 21.5 in. of rain to South San Francisco, 93% of the 23.1 in. normal.
How does South San Francisco weather compare with Montara?
Montara, 9.8 miles away, runs about 12°F cooler than South San Francisco on summer afternoons. It also has far more summer morning fog, 60% of morning hours compared with 20%.
What kind of place is South San Francisco?
South San Francisco fills a broad valley that opens east to the bay. San Bruno Mountain rises on its north side, and the Coast Range ridges stand to the west. The giant concrete letters on Sign Hill still spell out "South San Francisco The Industrial City" above downtown. The flats east of Highway 101 are better known today for biotech campuses and the Oyster Point waterfront, where a commuter ferry crosses to Oakland and Alameda.
What is South San Francisco weather like in November?
November at South San Francisco averages a high of 63°F and a low of 49°F, with 2.4 in. of rain over about 6 rainy days. Afternoon wind averages 6 mph.
More about South San Francisco 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 South San Francisco, Sign Hill (accessed 2026-10-27)
- BART, South San Francisco station (accessed 2026-10-27)
- San Francisco Bay Ferry, South San Francisco route (accessed 2026-10-27)
Rendered 2026-11-15T12:16:32.330Z.