Average Weather in April in Mill Valley California, United States
Daily high temperatures increase by 3°F, from 63°F to 66°F, rarely falling below 56°F or exceeding 76°F.
Daily low temperatures are around 49°F, rarely falling below 44°F or exceeding 54°F.
For reference, on September 11, the hottest day of the year, temperatures in Mill Valley typically range from 54°F to 73°F, while on January 1, the coldest day of the year, they range from 43°F to 54°F.
Average High and Low Temperature in April
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on April. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in April
Viña del Mar, Chile (5,902 miles away); Millicent, Australia (8,085 miles); and Lakes Entrance, Australia (7,732 miles) are the far-away foreign places with temperatures most similar to Mill Valley (view comparison).
The month of April in Mill Valley experiences decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 47% to 38%.
The clearest day of the month is April 28, with clear, mostly clear, or partly cloudy conditions 62% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 55%, while on July 20, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.
Cloud Cover Categories in April
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. In Mill Valley, the chance of a wet day over the course of April is very rapidly decreasing, starting the month at 18% and ending it at 9%.
For reference, the year's highest daily chance of a wet day is 31% on February 20, and its lowest chance is -0% on July 28.
Probability of Precipitation in April
The average sliding 31-day rainfall during April in Mill Valley is rapidly decreasing, starting the month at 2.0 inches, when it rarely exceeds 4.7 inches or falls below 0.1 inches, and ending the month at 0.8 inches, when it rarely exceeds 2.2 inches.
Average Monthly Rainfall in April
Over the course of April in Mill Valley, the length of the day is rapidly increasing. From the start to the end of the month, the length of the day increases by 1 hour, 7 minutes, implying an average daily increase of 2 minutes, 18 seconds, and weekly increase of 16 minutes, 6 seconds.
The shortest day of the month is April 1, with 12 hours, 38 minutes of daylight and the longest day is April 30, with 13 hours, 45 minutes of daylight.
Hours of Daylight and Twilight in April
The latest sunrise of the month in Mill Valley is 6:55 AM on April 1 and the earliest sunrise is 40 minutes earlier at 6:15 AM on April 30.
The earliest sunset is 7:33 PM on April 1 and the latest sunset is 27 minutes later at 8:00 PM on April 30.
Daylight saving time is observed in Mill Valley during 2018, but it neither starts nor ends during April, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:48 AM and sets 14 hours, 48 minutes later, at 8:35 PM, while on December 21, the shortest day of the year, it rises at 7:22 AM and sets 9 hours, 32 minutes later, at 4:54 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in April
The chance that a given day will be muggy in Mill Valley is essentially constant during April, remaining around 0% throughout.
For reference, on September 12, the muggiest day of the year, there are muggy conditions 0% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in April
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Mill Valley is essentially constant during April, remaining within 0.1 miles per hour of 9.1 miles per hour throughout.
For reference, on May 30, the windiest day of the year, the daily average wind speed is 9.4 miles per hour, while on October 21, the calmest day of the year, the daily average wind speed is 7.2 miles per hour.
Average Wind Speed in April
Wind Direction in April
Mill Valley 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 surface water temperature in Mill Valley is essentially constant during April, remaining around 53°F throughout.
Average Water Temperature in April
Temperatures in Mill Valley 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 in April
The average accumulated growing degree days in Mill Valley are gradually increasing during April, increasing by 173°F, from 280°F to 453°F, over the course of the month.
Growing Degree Days in April
The average daily incident shortwave solar energy in Mill Valley is increasing during April, rising by 1.3 kWh, from 5.6 kWh to 6.9 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in April
For the purposes of this report, the geographical coordinates of Mill Valley are 37.906 deg latitude, -122.545 deg longitude, and 269 ft elevation.
The topography within 2 miles of Mill Valley contains very significant variations in elevation, with a maximum elevation change of 1,368 feet and an average elevation above sea level of 332 feet. Within 10 miles contains very significant variations in elevation (2,569 feet). Within 50 miles contains large variations in elevation (3,809 feet).
The area within 2 miles of Mill Valley is covered by trees (47%) and artificial surfaces (38%), within 10 miles by water (47%) and trees (19%), and within 50 miles by water (44%) and grassland (18%).
This report illustrates the typical weather in Mill Valley year round, 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 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Mill Valley.
For each station, the records are corrected for the elevation difference between that station and Mill Valley 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 Mill Valley is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Mill Valley and a given station.
The stations contributing to this reconstruction are: Gnoss Field (40%, 27 kilometers, north); Naval Air Station Alameda (historical) (39%, 28 kilometers, southeast); and Buchanan Field Airport (20%, 44 kilometers, east).
Time zones for aiports and weather stations are provided by AskGeo.com .