South San Francisco in Summer
In summer (June, July and August), South San Francisco sees average daytime highs around 65°F and overnight lows near 55°F, with 0.2 in of rain over about 1 wet days across the season. It is the warmest season of the year and the driest season of the year.
Over the season highs climb from about 63°F in early June to 67°F by late August. The sky is clear or mostly clear about 58% of the time across summer, and the air most often feels dry.
Summer is South San Francisco's best season of the year to visit on our travel score. For the whole year in context, see South San Francisco's year-round climate.
- Avg daytime high
- 65°F
- warmest season of the year
- Avg overnight low
- 55°F
- Rainfall
- 0.2 in
- 1 wet days
- Avg wind
- 9 mph
- Travel score
- 7.7
- best season of the year
- Months
- Jun · Jul · Aug
Temperature in South San Francisco in Summer
Over the season highs climb from about 63°F in early June to 67°F by late August.
A typical summer day in South San Francisco reaches about 65°F and drops to 55°F overnight. The warmest of the three months is August, the coolest June.
South San Francisco weather by month
How the three summer months (June, July and August) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 55° / 47° | 4.3 | 10.1 | 9.7 | 3.7 |
| Feb | 57° / 48° | 4.4 | 9.3 | 10.5 | 4.0 |
| Mar | 58° / 49° | 3.2 | 9.3 | 11.7 | 4.5 |
| Apr | 59° / 50° | 1.5 | 5 | 12.9 | 5.4 |
| May | 61° / 52° | 0.7 | 2.8 | 14 | 6.3 |
| Jun | 64° / 54° | 0.2 | 0.8 | 14.6 | 7.5 |
| Jul | 65° / 55° | 0.0 | 0.1 | 14.3 | 7.8 |
| Aug | 66° / 56° | 0.0 | 0.1 | 13.5 | 7.9 |
| Sep | 67° / 56° | 0.1 | 0.4 | 12.3 | 8.1 |
| Oct | 65° / 54° | 0.9 | 3.1 | 11 | 7.5 |
| Nov | 60° / 50° | 2.2 | 6.1 | 10 | 5.4 |
| Dec | 56° / 47° | 4.2 | 10.1 | 9.4 | 3.8 |
Cloud cover in Summer
The sky is clear or mostly clear about 58% of the time across summer.
Chance of precipitation in Summer
South San Francisco gets around 0.2 in of rain over 1 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 9 mph across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 24 min in early June to 12 h 54 min by late August. The lit band spans sunrise to sunset each day.
Solar energy in Summer
Average shortwave solar energy reaching the ground each day across summer, about 7.3 kWh/m².
Hazard calendar for South San Francisco
None of South San Francisco's seasonal hazards peak in summer. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do.
South San Francisco's rainy season runs November–March, when most of the year's rain falls.
Is summer a good time to visit South San Francisco?
Our two travel scores rate summer for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
summer is one of the better times to visit South San Francisco for general sightseeing.
What to pack for South San Francisco in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, South San Francisco sees daytime highs around 65°F and nights near 55°F. Pack sun protection.
Sea temperature near South San Francisco in Summer
The nearest coast averages about 56°F across summer — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 12 mi away) is warmest in September at about 58°F and coldest in April near 53°F.
The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 53 | 54 | 54 | 53 | 53 | 54 | 56 | 58 | 58 | 57 | 56 | 54 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 53 | Bracing |
| Feb | 54 | Bracing |
| Mar | 54 | Bracing |
| Apr | 53 | Bracing |
| May | 53 | Bracing |
| Jun | 54 | Bracing |
| Jul | 56 | Bracing |
| Aug | 58 | Bracing |
| Sep | 58 | Bracing |
| Oct | 57 | Bracing |
| Nov | 56 | Bracing |
| Dec | 54 | Bracing |
UV index in South San Francisco in Summer
Clear-sky midday UV across summer averages around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in South San Francisco peaks around June 23 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 4 | 5 | 6 | 8 | 10 | 10 | 10 | 6 | 5 | 2 | 2 |
| Level | Moderate | Moderate | Moderate | High | Very high | Extreme | Extreme | Very high | High | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Moderate |
| Feb | 4 | Moderate |
| Mar | 5 | Moderate |
| Apr | 6 | High |
| May | 8 | Very high |
| Jun | 10 | Extreme |
| Jul | 10 | Extreme |
| Aug | 10 | Very high |
| Sep | 6 | High |
| Oct | 5 | High |
| Nov | 2 | Moderate |
| Dec | 2 | Moderate |
Air quality in South San Francisco in Summer
Average fine-particle pollution (PM2.5) through the year — so you can see where summer falls, not just the annual average.
Air quality in South San Francisco is worst in August — around 25 µg/m³ PM2.5 (moderate), about 2.5× the cleanest month (June, 10 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 15 | 18 | 16 | 12 | 10 | 10 | 11 | 25 | 17 | 20 | 18 | 13 |
| Level | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 15 | Moderate |
| Feb | 18 | Moderate |
| Mar | 16 | Moderate |
| Apr | 12 | Moderate |
| May | 10 | Good |
| Jun | 10 | Good |
| Jul | 11 | Good |
| Aug | 25 | Moderate |
| Sep | 17 | Moderate |
| Oct | 20 | Moderate |
| Nov | 18 | Moderate |
| Dec | 13 | Moderate |
Where is South San Francisco?
South San Francisco sits at 37.7°N, 122.4°W, 13 ft above sea level, in United States. The nearest listed city is San Bruno, 1.9 mi away.
Topography around South San Francisco
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of South San Francisco.
Within 2 miles, the terrain around South San Francisco has significant variations in elevation — a maximum elevation change of 1,194 ft around an average of 131 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 1,991 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,452 ft.
The land around South San Francisco is covered by artificial surfaces (61%) within 2 miles, water (51%) and artificial surfaces (24%) within 10 miles, and water (41%), trees (22%) and grassland (22%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for South San Francisco (37.6547°, -122.4077°, elevation 13 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.