Sunnyvale, CA weather in December
December in Sunnyvale: cool, with frequent rain. Highs 59°F, lows 42°F, about 11 days with rain. It is one of the coolest months in Sunnyvale.
- Normal high
- 59°F
- Normal low
- 42°F
- Wet days
- 11
- 2.5 in total
- Muggy days
- 0
- dew point 65°F+
How December changes from start to finish
| December 1 | December 31 | |
|---|---|---|
| Normal high | 61°F | 58°F |
| Normal low | 43°F | 42°F |
| Chance of a wet day | 33% | 34% |
| Sunrise / sunset | 7:03 am / 4:50 pm | 7:22 am / 4:59 pm |
| Daylight | 9.8 h | 9.6 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical December day
- 6 am48°Fdew point 43°F
- 9 am50°Fdew point 44°F
- Noon54°Fdew point 44°F
- 3 pm56°Fdew point 44°F
- 6 pm53°Fdew point 45°F
- 9 pm51°Fdew point 44°F
NOAA hourly normals (local standard time) from San Francisco Intl Airport (25 mi away); average wind 7 mph; clear or few clouds in 32% of daytime hours, mostly cloudy or overcast in 54%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F4 of 31
- Hot dayshigh 90°F or more0 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow11 of 31
- Notable rainat least 0.10 in6 of 31
- Freezing nightslow 32°F or below1 of 31
Average days per December, counted from daily records for each year 1991-2020.
Rain in December
Normal precipitation is 2.5 in; a dry December brings about 1.1 in and a wet one about 4.1 in (25th and 75th percentiles). About 1 day brings half an inch or more, and about 1 an inch or more. Snow is very rare.
How December varies from year to year
- Warmest December, 1991-20202011: average high 63°F
- Coolest December1998: average high 55°F
- Wettest December2014: 8.5 in
- Driest December2017: 0.08 in
- Highest reading78°F (December 5, 2003)
- Lowest reading26°F (December 24, 1998)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
December compared with November and January
| November | December | January | |
|---|---|---|---|
| Normal high | 66°F | 59°F | 59°F |
| Normal low | 46°F | 42°F | 42°F |
| Wet days | 9 | 11 | 11 |
| Comfortable days | 16 | 4 | 5 |
| Daylight | 10.2 h | 9.6 h | 9.9 h |
Highs change by -7°F from November and 0°F into January.
Nearby alternatives in December
- Warmer: Santa Maria, CA189 mi · high 64°F · 7 wet days
- Drier: Fresno, CA132 mi · high 55°F · 7 wet days
- Cooler: Yosemite Valley, CA137 mi · high 46°F · 9 wet days
How Sunnyvale ranks in December
- Normal high119th warmest of 378 cities; 33rd of 60 in California
- Wet days246th driest of 378
- Comfortable days141st most of 340
What to pack for Sunnyvale in December
- A rain jacket or umbrella – rain on about 11 days
Frost in December
The first fall frost typically comes around Dec 23; in 1 year in 10 it comes before Dec 3. All frost dates for Sunnyvale.
Heating and cooling
December has 449 heating degree days and 0 cooling degree days (base 65°F), 17% of the year's total heating and cooling demand.
Questions
How cold is Sunnyvale in December?
The normal high is 59°F and the normal low is 42°F. From 1991 to 2020 the coldest December reading was 26°F (December 24, 1998).
Does it rain a lot in Sunnyvale in December?
About 11 days in December have at least 0.01 in of precipitation, and the normal total is 2.5 in. The wettest December in 1991-2020 was in 2014 (8.5 in); the driest was in 2017 (0.08 in).
Is December a good time to visit Sunnyvale?
December ranks 12th of 12 months on our comfort score for Sunnyvale (47 out of 100). It has about 4 comfortable days. The best months are May, June and July.
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.