Average Weather in Janesville California, United States
In Janesville, the summers are warm, arid, and mostly clear and the winters are very cold, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 25°F to 86°F and is rarely below 14°F or above 93°F.
Based on the tourism score, the best time of year to visit Janesville for warm-weather activities is from late June to late August.
The hot season lasts for 3.1 months, from June 15 to September 18, with an average daily high temperature above 77°F. The hottest day of the year is July 29, with an average high of 86°F and low of 56°F.
The cold season lasts for 3.5 months, from November 18 to March 1, with an average daily high temperature below 49°F. The coldest day of the year is December 31, with an average low of 25°F and high of 40°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
Navacerrada, Spain (5,572 miles away); Yeşilova, Turkey (6,749 miles); and Aydıncık, Turkey (6,683 miles) are the far-away foreign places with temperatures most similar to Janesville (view comparison).
In Janesville, 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 Janesville begins around June 1 and lasts for 4.5 months, ending around October 17. On July 28, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 89% of the time, and overcast or mostly cloudy 11% of the time.
The cloudier part of the year begins around October 17 and lasts for 7.5 months, ending around June 1. On January 10, the cloudiest day of the year, the sky is overcast or mostly cloudy 57% of the time, and clear, mostly clear, or partly cloudy 43% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Janesville varies throughout the year.
The wetter season lasts 5.6 months, from October 30 to April 17, with a greater than 17% chance of a given day being a wet day. The chance of a wet day peaks at 32% on February 28.
The drier season lasts 6.4 months, from April 17 to October 30. The smallest chance of a wet day is 2% 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 25% on February 28.
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. Janesville experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 8.9 months, from September 19 to June 14, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 19, with an average total accumulation of 3.3 inches.
The rainless period of the year lasts for 3.1 months, from June 14 to September 19. The least rain falls around August 8, with an average total accumulation of 0.1 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Janesville experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.5 months, from November 13 to March 29, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 2, with an average total liquid-equivalent accumulation of 0.5 inches.
The snowless period of the year lasts for 7.5 months, from March 29 to November 13. The least snow falls around July 18, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Janesville varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 18 minutes of daylight; the longest day is June 21, with 15 hours, 3 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:31 AM on June 14, and the latest sunrise is 2 hours, 2 minutes later at 7:34 AM on November 3. The earliest sunset is at 4:35 PM on December 8, and the latest sunset is 4 hours, 0 minutes later at 8:36 PM on June 27.
Daylight saving time (DST) is observed in Janesville 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 Janesville, 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
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Janesville experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 4.2 months, from February 5 to June 13, with average wind speeds of more than 5.7 miles per hour. The windiest day of the year is April 5, with an average hourly wind speed of 6.4 miles per hour.
The calmer time of year lasts for 7.8 months, from June 13 to February 5. The calmest day of the year is August 6, with an average hourly wind speed of 5.0 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Janesville varies throughout the year.
The wind is most often from the south for 1.3 months, from February 5 to March 13 and for 1.7 weeks, from November 19 to December 1, with a peak percentage of 36% on February 23. The wind is most often from the west for 6.5 months, from March 13 to September 28, with a peak percentage of 58% on July 23. The wind is most often from the east for 1.7 months, from September 28 to November 19 and for 2.1 months, from December 1 to February 5, with a peak percentage of 35% on October 20.
Best Time of Year to Visit
To characterize how pleasant the weather is in Janesville 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 Janesville for general outdoor tourist activities is from late June to late August, with a peak score in the third 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 Janesville for hot-weather activities is from early July to mid August, with a peak score in the third week of July.
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
The growing season in Janesville typically lasts for 5.5 months (170 days), from around May 2 to around October 20, rarely starting before April 13 or after May 24, and rarely ending before September 28 or after November 8.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Janesville should appear around April 17, only rarely appearing before March 31 or after May 6.
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 3.4 months, from May 10 to August 23, with an average daily incident shortwave energy per square meter above 7.3 kWh. The brightest day of the year is July 1, with an average of 8.6 kWh.
The darker period of the year lasts for 3.5 months, from November 1 to February 15, with an average daily incident shortwave energy per square meter below 3.4 kWh. The darkest day of the year is December 19, with an average of 2.1 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Janesville are 40.297 deg latitude, -120.524 deg longitude, and 4,344 ft elevation.
The topography within 2 miles of Janesville contains very significant variations in elevation, with a maximum elevation change of 1,542 feet and an average elevation above sea level of 4,389 feet. Within 10 miles contains very significant variations in elevation (3,770 feet). Within 50 miles also contains extreme variations in elevation (6,949 feet).
The area within 2 miles of Janesville is covered by shrubs (61%), grassland (24%), and trees (12%), within 10 miles by shrubs (39%) and trees (34%), and within 50 miles by shrubs (52%) and trees (40%).
This report illustrates the typical weather in Janesville, 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 6 weather stations near enough to contribute to our estimation of the temperature and dew point in Janesville.
For each station, the records are corrected for the elevation difference between that station and Janesville 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 Janesville is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Janesville and a given station.
The stations contributing to this reconstruction are: Reno Stead Airport (30%, 89 kilometers, southeast); Blue Canyon-Nyack Airport (21%, 115 kilometers, south); Chico Municipal Airport (11%, 126 kilometers, southwest); Oroville Municipal Airport (11%, 130 kilometers, southwest); Alturas Municipal Airport (17%, 133 kilometers, north); and Redding Municipal Airport (10%, 152 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .