Climateby Month

Sunnyvale, CA climate by month

NOAA 1991-2020 normals · 124 ft elevation

Highs in Sunnyvale peak at 78°F in September (mild) and bottom out at 59°F in December (cool). The wettest month is February (about 11 wet days) and the driest is July (about 0). Snow is rare. The most comfortable time to visit is May, June and July.

Warmest month
78°F
September normal high
Coldest month
42°F
December normal low
Wet days a year
66
13.4 in of precipitation
Muggy days a year
0
dew point 65°F or higher

How warm is Sunnyvale?

Normal highs range from 59°F in December to 78°F in September.

40°50°60°70°80° January: normal high 59°F (15°C), low 42°F (6°C) 59° 42° February: normal high 62°F (17°C), low 45°F (7°C) March: normal high 65°F (18°C), low 47°F (8°C) April: normal high 68°F (20°C), low 49°F (9°C) May: normal high 72°F (22°C), low 53°F (12°C) June: normal high 76°F (24°C), low 56°F (13°C) July: normal high 77°F (25°C), low 59°F (15°C) August: normal high 77°F (25°C), low 59°F (15°C) September: normal high 78°F (26°C), low 57°F (14°C) 78° 57° October: normal high 74°F (23°C), low 53°F (12°C) November: normal high 66°F (19°C), low 46°F (8°C) December: normal high 59°F (15°C), low 42°F (6°C) JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Sunnyvale?

February has the most wet days (about 11); the year brings about 13 in of precipitation.

January: 11 wet days February: 11 wet days 11 March: 10 wet days April: 6 wet days May: 3 wet days June: 1 wet days July: 0 wet days 0 August: 0 wet days September: 1 wet days October: 4 wet days November: 9 wet days December: 11 wet days JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How humid is Sunnyvale?

Muggy days (dew point 65°F or higher) are rare in any month.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 0 muggy days June: 0 muggy days July: 0 muggy days August: 0 muggy days September: 0 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at N Y. Mineta Sn Jo Intl Apt, 6.2 mi E of the city center.

How much daylight?

Daylight ranges from about 9.6 hours in December to 14.7 hours in June.

January: 9.9 hours of daylight February: 10.8 hours of daylight March: 12.0 hours of daylight April: 13.2 hours of daylight May: 14.2 hours of daylight June: 14.7 hours of daylight 14.7 July: 14.4 hours of daylight August: 13.6 hours of daylight September: 12.4 hours of daylight October: 11.2 hours of daylight November: 10.2 hours of daylight December: 9.6 hours of daylight 9.6 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Sunnyvale, 1991-2020
MonthHighLowPrecip.Wet daysMuggy daysDaylight
January 59°F42°F 2.5 in11 0 9.9 h
February 62°F45°F 2.9 in11 0 10.8 h
March 65°F47°F 2.0 in10 0 12.0 h
April 68°F49°F 1.0 in6 0 13.2 h
May 72°F53°F 0.4 in3 0 14.2 h
June 76°F56°F 0.1 in1 0 14.7 h
July 77°F59°F 0.0 in0 0 14.4 h
August 77°F59°F 0.01 in0 0 13.6 h
September 78°F57°F 0.07 in1 0 12.4 h
October 74°F53°F 0.6 in4 0 11.2 h
November 66°F46°F 1.4 in9 0 10.2 h
December 59°F42°F 2.5 in11 0 9.6 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Sunnyvale

By our comfort score, the best months are May, June and July.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 50550
Feb 56860
Mar 681660
Apr 771830
May 882411
Jun 892302
Jul 892401
Aug 862302
Sep 792103
Oct 782321
Nov 671630
Dec 47460

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Sunnyvale

The last spring frost typically comes around Jan 6, and the first fall frost around Dec 23, leaving 353 frost-free days in a typical year.

Frost and freeze dates for Sunnyvale
Typical date1 year in 10
Last spring frost (32°F)Jan 6after Feb 4
First fall frost (32°F)Dec 23before Dec 3
Hard freeze (28°F)in about 14% of years; no typical date
Frost-free season353 daysunder 323 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Moffett Federal Airfield (USW00023244), NOAA 1991-2020 freeze probabilities. Frost dates for every city in California.

Hottest and coldest readings, 1991-2020

The highest reading was 106°F (June 14, 2000); the lowest was 26°F (December 24, 1998).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Sunnyvale

Similar climates elsewhere

Where the numbers come from

  • Temperature, rain and frost dates: Moffett Federal Airfield (USW00023244), 2.6 mi NNW of the city center, 39 ft (85 ft lower than the city). NOAA normals and daily records, 1991-2020.
  • Snowfall: Palo Alto (USC00046646), 7.7 mi NW of the city center, 25 ft (99 ft lower than the city). NOAA normals and daily records, 1991-2020.
  • Snow depth: Newark (USC00046144), 10 mi N of the city center, 10 ft (114 ft lower than the city). NOAA normals and daily records, 1991-2020.
  • Humidity and wind by hour and cloud cover: San Francisco Intl Airport (USW00023234), 25 mi NW of the city center, 8 ft (116 ft lower than the city). NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: N Y. Mineta Sn Jo Intl Apt (724945-23293), 6.2 mi E of the city center, 49 ft (75 ft lower than the city). Hourly observations, 1991-2020.

Distances from the city center (USGS). Methodology · Report an error