Sunnyvale climate

Name: Sunnyvale
Address: US

Sunnyvale is warmest in August, with average highs of 28 °C, and coldest in January, when nights average 6.3 °C. February is the wettest month (126 mm) and July the driest (0.7 mm). Figures are 1991–2020 climate normals.

Across a full year Sunnyvale averages 620 mm of rain, 105 days above 25 °C and 0 days below freezing.

United States · 39 m elevation · population 155,805 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month August 28 °C
Coldest month January 6.3 °C
Driest month July 1 mm
Wettest month February 126 mm
Least cloud September 21 % cloud
Hottest on record September 43 °C
Coldest on record January -2.1 °C
Warmest sea August 15 °C

What to expectSunnyvale through the year

Sunnyvale has a clear annual cycle: average daily highs run from 15 °C in January to 28 °C in August, a swing of 10 °C in mean temperature across the year.

Counted across a normal year, 105 days a year reach 25 °C, 36 of them reach 30 °C, 0 nights drop below freezing. The warmest reading in the 1991–2020 record is 43 °C, in September.

Rain is strongly seasonal. February averages 126 mm against 1 mm in July — 169 times as much. Planning around the dry months matters more here than planning around temperature.

The sea off Sunnyvale is warmest in August at 15 °C and coldest in April at 12 °C. Sea temperature lags the air by a month or two, which is why late summer swims warmer than early summer at the same air temperature.

Month by month

Month	Avg high	Rainfall	Cloud
January	14.6 °C	121 mm	58 %
February	15.8 °C	126 mm	58 %
March	17.4 °C	93 mm	57 %
April	19.4 °C	46 mm	49 %
May	22.1 °C	21 mm	42 %
June	25.5 °C	4 mm	28 %
July	27.5 °C	1 mm	22 %
August	27.7 °C	1 mm	22 %
September	27.4 °C	2 mm	21 %
October	23.8 °C	29 mm	31 %
November	18.0 °C	58 mm	47 %
December	14.2 °C	116 mm	55 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days above 30 °C
January	14.6 °C	6.3 °C	9.8 °C	24.5 °C	-2.1 °C	0	0
February	15.8 °C	7.2 °C	10.8 °C	25.5 °C	-0.6 °C	0	0
March	17.4 °C	8.5 °C	12.1 °C	28.4 °C	1.7 °C	1	0
April	19.4 °C	9.4 °C	13.4 °C	34.9 °C	2.5 °C	4	1
May	22.1 °C	11.1 °C	15.6 °C	36.9 °C	4.8 °C	8	2
June	25.5 °C	12.9 °C	18.1 °C	40.8 °C	5.9 °C	15	6
July	27.5 °C	14.6 °C	19.9 °C	41.7 °C	8.3 °C	22	8
August	27.7 °C	15.0 °C	20.0 °C	39.7 °C	10.0 °C	23	8
September	27.4 °C	15.4 °C	19.9 °C	42.6 °C	9.1 °C	20	8
October	23.8 °C	13.4 °C	17.5 °C	38.0 °C	5.0 °C	12	3
November	18.0 °C	9.7 °C	13.0 °C	29.2 °C	1.9 °C	1	0
December	14.2 °C	6.8 °C	9.9 °C	21.7 °C	-2.1 °C	0	0

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind	Sea temp
January	121 mm	9	9.9 h/day	58 %	80 %	12 km/h	12.2 °C
February	126 mm	10	11 h/day	58 %	79 %	13 km/h	12.3 °C
March	93 mm	9	12 h/day	57 %	77 %	13 km/h	12.3 °C
April	46 mm	6	13 h/day	49 %	72 %	15 km/h	12.0 °C
May	21 mm	3	14 h/day	42 %	69 %	14 km/h	12.2 °C
June	4 mm	1	15 h/day	28 %	64 %	14 km/h	12.9 °C
July	1 mm	0	14 h/day	22 %	64 %	12 km/h	14.1 °C
August	1 mm	0	14 h/day	22 %	66 %	12 km/h	14.9 °C
September	2 mm	1	12 h/day	21 %	65 %	12 km/h	14.9 °C
October	29 mm	3	11 h/day	31 %	66 %	12 km/h	14.2 °C
November	58 mm	6	10 h/day	47 %	74 %	11 km/h	13.4 °C
December	116 mm	9	9.6 h/day	55 %	78 %	12 km/h	12.5 °C

How Sunnyvale compares

The same four figures for nearby destinations, so the numbers above have something to be read against. Summer high is the warmest month's average high; winter low is the coldest month's average low.

Destination	Summer high	Winter low	Rain per year	Days above 25 °C
Sunnyvale	28 °C	6.3 °C	620 mm	105
San Jose · United States	29 °C	6.4 °C	627 mm	122
Fremont · United States	28 °C	6.2 °C	487 mm	105
Oakland · United States	26 °C	6.0 °C	498 mm	87
San Francisco · United States	23 °C	6.5 °C	490 mm	26

Where Sunnyvale ranks

Ranking	Position	Value
Places with the best weather in North America in October	1stof 50	97/100
Places with the best weather in North America in May	6thof 50	96/100
The driest places in North America in September	8thof 50	2.4 mm
The driest places in North America in July	10thof 50	0.7 mm
Places with the best weather in North America in June	11thof 50	94/100
Places with the best weather in North America in July	17thof 50	88/100

Planning a trip? See the best time to visit Sunnyvale.

QuestionsCommon questions about Sunnyvale’s climate

When is the best time to visit Sunnyvale?

That depends on what you want, so the honest answer is a comparison rather than a single month. July, August, September sit closest to 20 °C on average, August is the warmest month and July the driest. The month-by-month table above has the full picture.

How hot does Sunnyvale get?

In August, the warmest month, daily highs average 28 °C. About 36 days a year pass 30 °C. The highest value in the 1991–2020 record is 43 °C.

How cold does it get in winter?

Nights average 6.3 °C in January, the coldest month. A normal year has 0 nights below freezing.

Which month is wettest in Sunnyvale?

February, averaging 126 mm over 10 days with rain. The driest month is July with 1 mm. The year as a whole averages 620 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in Sunnyvale rather than what any particular week will bring. Individual years can differ substantially from the normal.

Data sources and method

ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
Open-Meteo — Open-Meteo.com. CC BY 4.0
NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
GeoNames — GeoNames.org. CC BY 4.0

Normal period: 1991–2020
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.