Average Weather in April in Riverdale California, United States
Daily high temperatures increase by 8°F, from 73°F to 81°F, rarely falling below 62°F or exceeding 93°F.
Daily low temperatures increase by 5°F, from 47°F to 52°F, rarely falling below 39°F or exceeding 59°F.
For reference, on July 18, the hottest day of the year, temperatures in Riverdale typically range from 65°F to 98°F, while on December 25, the coldest day of the year, they range from 38°F to 55°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
The month of April in Riverdale experiences gradually decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 38% to 31%.
The clearest day of the month is April 30, with clear, mostly clear, or partly cloudy conditions 69% of the time.
For reference, on February 21, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 48%, while on August 8, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.
Cloud Cover Categories in April
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Riverdale, the chance of a wet day over the course of April is rapidly decreasing, starting the month at 14% and ending it at 7%.
For reference, the year's highest daily chance of a wet day is 25% on February 20, and its lowest chance is 0% on August 9.
Probability of Precipitation in April
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during April in Riverdale is decreasing, starting the month at 1.2 inches, when it rarely exceeds 3.3 inches or falls below 0.1 inches, and ending the month at 0.5 inches, when it rarely exceeds 1.4 inches.
Average Monthly Rainfall in April
Over the course of April in Riverdale, 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, 3 minutes, implying an average daily increase of 2 minutes, 11 seconds, and weekly increase of 15 minutes, 15 seconds.
The shortest day of the month is April 1, with 12 hours, 36 minutes of daylight and the longest day is April 30, with 13 hours, 40 minutes of daylight.
Hours of Daylight and Twilight in April
The latest sunrise of the month in Riverdale is 6:45 AM on April 1 and the earliest sunrise is 38 minutes earlier at 6:07 AM on April 30.
The earliest sunset is 7:21 PM on April 1 and the latest sunset is 25 minutes later at 7:46 PM on April 30.
Daylight saving time is observed in Riverdale 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 5:41 AM and sets 14 hours, 39 minutes later, at 8:20 PM, while on December 21, the shortest day of the year, it rises at 7:07 AM and sets 9 hours, 40 minutes later, at 4:47 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in April
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 chance that a given day will be muggy in Riverdale is essentially constant during April, remaining around 0% throughout.
For reference, on July 22, the muggiest day of the year, there are muggy conditions 1% 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
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 Riverdale is gradually increasing during April, increasing from 6.7 miles per hour to 7.6 miles per hour over the course of the month.
For reference, on May 30, the windiest day of the year, the daily average wind speed is 8.5 miles per hour, while on January 13, the calmest day of the year, the daily average wind speed is 4.8 miles per hour.
Average Wind Speed in April
Wind Direction in April
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
The growing season in Riverdale typically lasts for 10 months (303 days), from around February 1 to around December 1, rarely starting after March 3, or ending before November 13.
The month of April in Riverdale is reliably fully within the growing season.
Time Spent in Various Temperature Bands and the Growing Season in April
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
The average accumulated growing degree days in Riverdale are increasing during April, increasing by 363°F, from 418°F to 781°F, over the course of the month.
Growing Degree Days in April
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 in Riverdale is increasing during April, rising by 1.3 kWh, from 5.9 kWh to 7.2 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 Riverdale are 36.431 deg latitude, -119.860 deg longitude, and 220 ft elevation.
The topography within 2 miles of Riverdale is essentially flat, with a maximum elevation change of 13 feet and an average elevation above sea level of 220 feet. Within 10 miles is also essentially flat (79 feet). Within 50 miles is essentially flat (5,194 feet).
The area within 2 miles of Riverdale is covered by cropland (98%), within 10 miles by cropland (98%), and within 50 miles by cropland (59%) and grassland (28%).
This report illustrates the typical weather in Riverdale 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 Riverdale.
For each station, the records are corrected for the elevation difference between that station and Riverdale 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 Riverdale is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Riverdale and a given station.
The stations contributing to this reconstruction are: Lemoore Naval Air Station (Reeves Field) (62%, 14 kilometers, southwest); Hanford Municipal Airport (26%, 24 kilometers, southeast); and Fresno Air Terminal Airport (12%, 41 kilometers, north).
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 .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.