Foster City weather in August

In August, Foster City sees average daytime highs of 74°F and overnight lows near 57°F, with 0.0 in of rain across 0.1 wet days and about 13.4 hours of daylight. It is the 2nd-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 74°F through the month. The sky is clear or mostly clear about 80% of the time in August, and the air most often feels comfortable.

Daylight stretches from about 14 hours at the start of August to 12 h 54 min by month's end. Set against the rest of the year, August is Foster City's 3rd-clearest and 8th-windiest month. For the whole year in context, see Foster City's year-round climate.

Daytime high
74°
2nd warmest
Overnight low
57°
12th coldest
Rainfall
0.0 in
0.1 wet days
Daylight
13 h 30 min
5:29 AM – 6:57 PM
Cloud cover
24%
3rd clearest
Wind
5 mph
8th windiest
Solar energy
6.81 kWh/m²
Travel score
9.2
out of 10

Foster City is city in San Mateo County, California, United States.

Density
651/km²
people per km²
Founded
1971

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in August

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 74°F through the month.

A typical August day in Foster City reaches about 74°F in the afternoon and slips back to 57°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 82°F. Set against its neighbours, August runs on par with July and on par with September.

50°60°70°80°151015202531
Avg high (°F)Avg low (°F)
17357
27357
37357
47357
57357
67357
77357
87357
97357
107357
117357
127457
137457
147457
157457
167457
177457
187457
197457
207457
217457
227457
237457
247457
257457
267457
277457
287457
297457
307457
317457

Foster City weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan57° / 45°3.99.49.74.1
Feb59° / 47°4.29.310.64.5
Mar61° / 48°3.29.111.75.3
Apr63° / 49°1.65.612.96.4
May66° / 52°0.83.3147.4
Jun70° / 54°0.20.914.58.5
Jul73° / 56°0.00.214.39.1
Aug74° / 57°0.00.113.49.2
Sep74° / 57°0.10.412.39.2
Oct71° / 54°0.93118.2
Nov63° / 49°2.06106.1
Dec57° / 46°3.79.39.54.1

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 80% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 10% of August, with mostly cloudy or overcast conditions the remaining 11%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
18911
28911
38812
48812
58812
68713
78713
88713
98713
108812
118812
128812
138812
148812
158812
168812
178911
188911
198911
209010
219010
229010
239010
24919
25919
26928
27937
28937
29937
30937
31937

Chance of precipitation in August

Any precipitation

Foster City gets around 0.0 in of rain over 0.1 wet days in August. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 0% and peaks near 1% on the wettest days.

0%10%20%30%151015202531
Rain chance (%)
10
20
30
40
50
60
70
80
90
100
110
120
130
141
151
161
171
181
191
201
211
221
231
240
250
260
270
280
290
300
310

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

Most of August feels comfortable — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, August lands in the comfortable band about 52% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
149501
249501
349501
448511
547521
647521
746531
846522
945532
1045532
1144542
1244542
1344542
1444542
1544542
1644542
1744542
1845532
1945532
2045523
2145523
2245523
2344533
2444533
2544533
2644533
2744524
2844524
2945514
3045514
3146504

Wind in August

Winds average 5 mph in August.

Across August, daily wind ranges from about 5 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 hours at the start of August to 12 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over August. Sunrise moves from 5:16 AM to 5:42 AM, and sunset from 7:14 PM to 6:36 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.05:167:14
213.95:177:13
313.95:187:12
413.95:197:11
513.85:207:10
613.85:217:09
713.85:227:08
813.75:227:07
913.75:237:05
1013.75:247:04
1113.65:257:03
1213.65:267:02
1313.65:277:01
1413.55:286:59
1513.55:296:58
1613.55:296:57
1713.45:306:56
1813.45:316:54
1913.35:326:53
2013.35:336:52
2113.35:346:50
2213.25:356:49
2313.25:366:47
2413.25:366:46
2513.15:376:45
2613.15:386:43
2713.05:396:42
2813.05:406:40
2913.05:416:39
3012.95:426:37
3112.95:426:36

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 6.81 kWh/m².

For context, solar energy here swings from a low near 2.27 kWh/m² to a high of 7.76 kWh/m² in June across the year — August's 6.81 kWh/m² falls in the middle.

02468151015202531
Solar energy (kWh/m²)Level
17.2Intense
27.2Intense
37.1Intense
47.1Intense
57.1Intense
67.1Intense
77.0Intense
87.0Intense
97.0Intense
107.0Intense
117.0Intense
126.9Intense
136.9Intense
146.9Intense
156.8Intense
166.8Intense
176.8Intense
186.8Intense
196.7Intense
206.7Intense
216.7Intense
226.7Intense
236.6Intense
246.6Intense
256.6Intense
266.5Intense
276.5Intense
286.5Intense
296.5Intense
306.4Intense
316.4Intense
Planning a trip in August

Hazard calendar for Foster City

In seasonPeak

None of Foster City's seasonal hazards are active in August. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Foster City's rainy season runs November–March, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is August a good time to visit Foster City?

Our two travel scores rate August for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

9.2
Sightseeing
1st-best month of the year
7.2
Beach & pool
2nd-best month of the year

August is one of the better times to visit Foster City for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Foster City in August

From August's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In August, Foster City sees daytime highs around 74°F and nights near 57°F. Pack sun protection. Worth having: light clothes.

sun protectionlight clothes

Sea temperature near Foster City in August

The nearest coast averages about 59°F in August — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 14 mi away) is warmest in August at about 59°F and coldest in April near 54°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

52°54°56°58°60°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°F)Comfort
Jan54Bracing
Feb54Bracing
Mar54Bracing
Apr54Bracing
May54Bracing
Jun55Bracing
Jul57Bracing
Aug59Bracing
Sep59Bracing
Oct58Bracing
Nov56Bracing
Dec55Bracing

UV index in Foster City in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks 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 Foster City 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.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJun 23UV 10Dec 15UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar5Moderate
Apr6High
May8Very high
Jun10Extreme
Jul10Extreme
Aug10Very high
Sep6High
Oct5High
Nov2Moderate
Dec2Moderate

Air quality in Foster City in August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August falls, not just the annual average.

Air quality in Foster City 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).

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateAug 1824 µg/m³Jun 1110 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb18Moderate
Mar16Moderate
Apr12Moderate
May10Good
Jun10Good
Jul11Good
Aug25Moderate
Sep17Moderate
Oct20Moderate
Nov18Moderate
Dec13Moderate
Location & terrain

Where is Foster City?

Foster City sits at 37.6°N, 122.3°W, 7 ft above sea level, in United States. The nearest listed city is Belmont, 2.5 mi away.

Topography around Foster City

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Foster City.

Within 2 miles, the terrain around Foster City has only modest variations in elevation — a maximum elevation change of 66 ft around an average of 7 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,457 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,452 ft.

The land around Foster City is covered by artificial surfaces (49%) and water (36%) within 2 miles, water (46%) and trees (28%) within 10 miles, and water (39%), trees (23%) and grassland (22%) within 50 miles.

2 miles
66 ft
10 miles
2,457 ft
50 miles
4,452 ft
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
August weather nearby: Belmont 2.5 mi · San Mateo 3.1 mi · San Carlos 3.7 mi · Redwood City 5.6 mi · Burlingame 5.6 mi · Millbrae 6.8 mi · Menlo Park 8.7 mi · San Bruno 9.3 mi

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
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

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 Foster City (37.5585°, -122.2711°, elevation 7 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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).