Photo: The Sands of Time 0 · CC BY-SA 4.0Afternoon heat in Sunnyvale trails that of 94% of U.S. towns
On a normal January night the air cools to about 41°. A year here swings 39° from midwinter lows to midsummer highs. It is a dry place: less rain and snow fall here than on 92% of U.S. towns. For walks and days out, the stretch from February to November brings highs of 63–80°.
A year in Sunnyvale at a glance
Each month’s typical high and low, and what it brings.
What stands out about Sunnyvale’s climate
Compared with towns across the U.S., with Sunnyvale’s place in California beside it.
What a year in Sunnyvale feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Frost and day counts come from NOAA’s station at Moffett Federal Airfield, CA, 1.8 miles from the city’s center point, at about the same height.
The 2023 USDA map puts Sunnyvale’s center in zone 10a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 30°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 16 inches of rain a year
February is the wettest month and July the driest. Rain falls on about 56 days a year. Snow is rare: about 0.0" in a normal year at Palo Alto, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Sunnyvale
84% of the work is heating. Months averaging under 55° run from December through February.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Moffett Federal Airfield, CA.
Living with Sunnyvale’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 10a. Frost comes about 7 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: February, March, April, May, June, July, August, September, October and November. 16 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Sunnyvale from natural hazards, earthquakes are the largest share (68%); heat waves, cold waves, winter storms and ice storms together are 2%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Sunnyvale and its neighbors
Cupertino has the coldest January nights next door (39°, 2° colder) and San Jose the hottest July afternoons (86°, 6° warmer). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Sunnyvale’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Sunnyvale, CA | 41° | 80° | 16" | 0.0" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Poulsbo, WA | 35° | 75° | 33" | 3.0" |
| Winston, OR | 37° | 86° | 33" | 0.0" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Sunnyvale averaged 1.8° warmer than the 1900s. The biggest change is in August (+2.2°).
A bigger shift than in 80% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods. In a city of 157,000 people, part of the change is the city itself: pavement and buildings hold heat (the urban heat island).
How Sunnyvale compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Sunnyvale’s place among California’s.
Sunnyvale weather by month
Highs, lows and precipitation from NOAA’s grid at Sunnyvale’s center; snow, wet days and snow on the ground from Palo Alto, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 60° | 41° | 3.2" | 0.0" | 10 | 0 | 47° – 54° |
| February | 63° | 43° | 3.4" | 0.0" | 10 | 0 | 49° – 58° |
| March | 66° | 45° | 2.5" | 0.0" | 8 | 0 | 51° – 61° |
| April | 69° | 47° | 1.2" | 0.0" | 5 | 0 | 54° – 61° |
| May | 73° | 51° | 0.5" | 0.0" | 3 | 0 | 58° – 66° |
| June | 78° | 54° | 0.1" | 0.0" | 1 | 0 | 62° – 68° |
| July | 80° | 56° | 0.0" | 0.0" | 0 | 0 | 65° – 71° |
| August | 80° | 56° | 0.0" | 0.0" | 0 | 0 | 65° – 72° |
| September | 79° | 55° | 0.1" | 0.0" | 1 | 0 | 64° – 71° |
| October | 75° | 51° | 0.7" | 0.0" | 3 | 0 | 60° – 69° |
| November | 66° | 45° | 1.6" | 0.0" | 6 | 0 | 49° – 59° |
| December | 59° | 41° | 3.1" | 0.0" | 10 | 0 | 46° – 55° |
| Year | 71° | 49° | 16.3" | 0.0" | 56 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 51° to 61°. July is the most reliable, staying within 6°.
Where Sunnyvale’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Sunnyvale’s center.
- Snow: Palo Alto, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Moffett Federal Airfield, CA, 1.8 miles from the city’s center point, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Sunnyvale’s climate
What is the weather like in Sunnyvale?
A typical July afternoon reaches 80°, a January night drops to 41°, and snow is almost unheard of. Milder January nights than 90% of U.S. towns; cooler July afternoons than 94% of U.S. towns.
How cold does it get in Sunnyvale in winter?
December nights average 41°. About 2 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 46°.
How much snow does Sunnyvale get?
About 0.0 inches in a normal winter at Palo Alto, CA, so most winters see none.
How hot does it get in Sunnyvale?
July, with a typical high of 80° and a low of 56°. About 9 days a year reach 90° (Moffett Federal Airfield, CA).
When is the first and last frost in Sunnyvale?
There is no reliable frost date: a 32° night comes in about 70% of winters at Moffett Federal Airfield, CA, so most years bring a freeze but some pass without one.
What growing zone is Sunnyvale in?
Zone 10a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 30°.
What is the best time of year to visit Sunnyvale?
By one simple rule (highs of 62–84° and lows of 40° or more), February, March, April, May, June, July, August, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Sunnyvale getting warmer?
Yes: 1991–2020 averaged 1.8° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 80% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Sunnyvale.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.