Average Weather in Santa Rosa California, United States
In Santa Rosa, the temperature typically varies from 37°F to 84°F over the course of the year, and is rarely below 28°F or above 96°F.
The warm season lasts for 4.3 months, from June 2 to October 11, with an average daily high temperature above 78°F. The hottest day of the year is July 4, with an average high of 84°F and low of 52°F.
The cool season lasts for 2.5 months, from November 26 to February 13, with an average daily high temperature below 61°F. The coldest day of the year is January 1, with an average low of 37°F and high of 55°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
The length of the day in Santa Rosa varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 29 minutes of daylight; the longest day is June 21, with 14 hours, 51 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, 55 minutes later at 7:40 AM on November 4. The earliest sunset is at 4:49 PM on December 6, and the latest sunset is 3 hours, 49 minutes later at 8:38 PM on June 27.
Daylight saving time (DST) is observed in Santa Rosa during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
In Santa Rosa, 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 Santa Rosa begins around May 17 and lasts for 5.2 months, ending around October 23. On July 27, 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 23 and lasts for 6.8 months, ending around May 17. On January 10, the cloudiest day of the year, the sky is overcast or mostly cloudy 58% of the time, and clear, mostly clear, or partly cloudy 42% of the time.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Santa Rosa varies significantly throughout the year.
The wetter season lasts 5.3 months, from October 31 to April 10, with a greater than 17% chance of a given day being a wet day. The chance of a wet day peaks at 34% on February 20.
The drier season lasts 6.7 months, from April 10 to October 31. The smallest chance of a wet day is 0% on July 25.
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 34% 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 in the year. Santa Rosa experiences very significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 8.1 months, from September 28 to May 30, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 16, with an average total accumulation of 5.7 inches.
The rainless period of the year lasts for 3.9 months, from May 30 to September 28. The least rain falls around July 29, with and average total accumulation of 0.0 inches.
Average Monthly Rainfall
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
The perceived humidity level in Santa Rosa, 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
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.The average hourly wind speed in Santa Rosa does not vary significantly over the course of the year, remaining within 0.4 miles per hour of 3.9 miles per hour throughout.
Average Wind Speed
The predominant average hourly wind direction in Santa Rosa varies throughout the year.
The wind is most often from the west for 7.8 months, from February 27 to October 20, with a peak percentage of 82% on July 31. The wind is most often from the north for 4.2 months, from October 20 to February 27, with a peak percentage of 46% on December 10.
Santa Rosa 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 13 to October 30, with an average temperature above 56°F. The day of the year with the warmest water is September 22, with an average temperature of 57°F.
The time of year with cooler water lasts for 3.1 months, from March 25 to June 29, with an average temperature below 53°F. The day of the year with the coolest water is May 12, with an average temperature of 52°F.
Average Water Temperature
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy experiences very significant seasonal variation over the course of the year.
The brighter period of the year lasts for 3.5 months, from May 8 to August 25, with an average daily incident shortwave energy per square meter above 7.1 kWh. The brightest day of the year is June 27, with an average of 8.5 kWh.
The darker period of the year lasts for 3.6 months, from November 3 to February 20, with an average daily incident shortwave energy per square meter below 3.3 kWh. The darkest day of the year is December 26, with an average of 2.0 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Santa Rosa are 38.440 deg latitude, -122.714 deg longitude, and 157 ft elevation.
The topography within 2 miles of Santa Rosa contains only modest variations in elevation, with a maximum elevation change of 433 feet, and an average elevation above sea level of 170 feet. Within 10 miles contains large variations in elevation (2,684 feet). Within 50 miles contains extreme variations in elevation (4,701 feet).
The area within 2 miles of Santa Rosa is covered by artificial surfaces (96%), within 10 miles by grassland (30%) and cropland (27%), and within 50 miles by water (29%) and shrubs (23%).
This report illustrates the typical weather in Santa Rosa, 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 Santa Rosa.
For each station, the records are corrected for the elevation difference between that station and Santa Rosa 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 Santa Rosa is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Santa Rosa and a given station.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for aiports and weather stations are provided by AskGeo.com .