Average Weather in Sunnyvale California, United States
In Sunnyvale, the summers are long, warm, arid, and mostly clear and the winters are short, cold, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 44°F to 77°F and is rarely below 36°F or above 87°F.
Based on the tourism score, the best time of year to visit Sunnyvale for warm-weather activities is from late June to late September.
The warm season lasts for 4.4 months, from June 3 to October 16, with an average daily high temperature above 73°F. The hottest day of the year is September 11, with an average high of 77°F and low of 59°F.
The cool season lasts for 2.4 months, from November 29 to February 10, with an average daily high temperature below 61°F. The coldest day of the year is December 31, with an average low of 44°F and high of 58°F.
Average High and Low Temperature
Average Hourly Temperature
Vicuña, Chile (5,724 miles away); São Francisco de Paula, Brazil (6,536 miles); and Amor, Portugal (5,636 miles) are the far-away foreign places with temperatures most similar to Sunnyvale (view comparison).
In Sunnyvale, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Sunnyvale begins around May 23 and lasts for 5.1 months, ending around October 26. On July 21, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 92% of the time, and overcast or mostly cloudy 8% of the time.
The cloudier part of the year begins around October 26 and lasts for 6.9 months, ending around May 23. On January 11, the cloudiest day of the year, the sky is overcast or mostly cloudy 55% of the time, and clear, mostly clear, or partly cloudy 45% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Sunnyvale varies significantly throughout the year.
The wetter season lasts 5.2 months, from November 5 to April 10, with a greater than 15% chance of a given day being a wet day. The chance of a wet day peaks at 30% on February 20.
The drier season lasts 6.8 months, from April 10 to November 5. The smallest chance of a wet day is 0% on July 19.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 30% on February 20.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Sunnyvale experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 7.3 months, from October 4 to May 13, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 15, with an average total accumulation of 3.8 inches.
The rainless period of the year lasts for 4.7 months, from May 13 to October 4. The least rain falls around July 30, with an average total accumulation of 0.0 inches.
Average Monthly Rainfall
The length of the day in Sunnyvale varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 35 minutes of daylight; the longest day is June 21, with 14 hours, 45 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:46 AM on June 13, and the latest sunrise is 1 hour, 48 minutes later at 7:35 AM on November 3. The earliest sunset is at 4:50 PM on December 6, and the latest sunset is 3 hours, 43 minutes later at 8:32 PM on June 28.
Daylight saving time (DST) is observed in Sunnyvale during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level in Sunnyvale, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.
Humidity Comfort Levels
The average hourly wind speed in Sunnyvale experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 4.9 months, from March 10 to August 5, with average wind speeds of more than 7.7 miles per hour. The windiest day of the year is June 6, with an average hourly wind speed of 8.9 miles per hour.
The calmer time of year lasts for 7.1 months, from August 5 to March 10. The calmest day of the year is October 21, with an average hourly wind speed of 6.5 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Sunnyvale varies throughout the year.
The wind is most often from the west for 9.0 months, from February 13 to November 12, with a peak percentage of 92% on August 11. The wind is most often from the north for 3.0 months, from November 12 to February 13, with a peak percentage of 33% on January 1.
Sunnyvale is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average water temperature experiences some seasonal variation over the course of the year.
The time of year with warmer water lasts for 2.5 months, from August 1 to October 19, with an average temperature above 57°F. The day of the year with the warmest water is September 15, with an average temperature of 58°F.
The time of year with cooler water lasts for 5.7 months, from December 22 to June 11, with an average temperature below 54°F. The day of the year with the coolest water is May 2, with an average temperature of 53°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Sunnyvale throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Sunnyvale for general outdoor tourist activities is from late June to late September, with a peak score in the last week of July.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Sunnyvale for hot-weather activities is from late June to mid September, with a peak score in the last week of July.
Temperatures in Sunnyvale are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season
Growing Degree Days
The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.6 months, from May 7 to August 25, with an average daily incident shortwave energy per square meter above 7.2 kWh. The brightest day of the year is June 27, with an average of 8.4 kWh.
The darker period of the year lasts for 3.5 months, from November 4 to February 18, with an average daily incident shortwave energy per square meter below 3.5 kWh. The darkest day of the year is December 23, with an average of 2.2 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Sunnyvale are 37.369 deg latitude, -122.036 deg longitude, and 112 ft elevation.
The topography within 2 miles of Sunnyvale contains only modest variations in elevation, with a maximum elevation change of 187 feet and an average elevation above sea level of 121 feet. Within 10 miles contains only modest variations in elevation (3,074 feet). Within 50 miles contains large variations in elevation (4,318 feet).
The area within 2 miles of Sunnyvale is covered by artificial surfaces (100%), within 10 miles by artificial surfaces (58%) and trees (11%), and within 50 miles by water (37%) and grassland (19%).
This report illustrates the typical weather in Sunnyvale, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Sunnyvale.
For each station, the records are corrected for the elevation difference between that station and Sunnyvale according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Sunnyvale is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Sunnyvale and a given station.
Time zones for aiports and weather stations are provided by AskGeo.com .