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Average Weather in April in Rosemont California, United States

Daily low temperatures increase by 4°F, from 46°F to 50°F, rarely falling below 40°F or exceeding 56°F.

For reference, on July 19, the hottest day of the year, temperatures in Rosemont typically range from 60°F to 94°F, while on December 31, the coldest day of the year, they range from 39°F to 53°F.

Average High and Low Temperature in April

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

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

Average Hourly Temperature in April in Rosemont1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM4 AM8 AM12 PM4 PM8 PM12 AMMarMaycoldcoldcoolcoolcomfortablewarm
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

La Albuera, Spain (5,683 miles away) and Al Jīzah, Jordan (7,377 miles) are the far-away foreign places with temperatures most similar to Rosemont (view comparison).

Clouds

The month of April in Rosemont 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 February 6, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 56%, while on July 29, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 91%.

Cloud Cover Categories in April

Cloud Cover Categories in April in Rosemont181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMayApr 153%Apr 153%Apr 3062%Apr 3062%Apr 1157%Apr 1157%Apr 2158%Apr 2158%clearmostly clearmostly cloudyovercastpartly cloudy
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Rosemont, the chance of a wet day over the course of April is very rapidly decreasing, starting the month at 19% and ending it at 10%.

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 21.

Probability of Precipitation in April

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

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 Rosemont is rapidly decreasing, starting the month at 2.2 inches, when it rarely exceeds 4.9 inches or falls below 0.2 inches, and ending the month at 1.0 inches, when it rarely exceeds 2.5 inches.

Average Monthly Rainfall in April

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

Over the course of April in Rosemont, 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, 8 minutes, implying an average daily increase of 2 minutes, 21 seconds, and weekly increase of 16 minutes, 28 seconds.

The shortest day of the month is April 1, with 12 hours, 40 minutes of daylight and the longest day is April 30, with 13 hours, 48 minutes of daylight.

Hours of Daylight and Twilight in April

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The latest sunrise of the month in Rosemont is 6:49 AM on April 1 and the earliest sunrise is 41 minutes earlier at 6:09 AM on April 30.

The earliest sunset is 7:29 PM on April 1 and the latest sunset is 28 minutes later at 7:56 PM on April 30.

Daylight saving time is observed in Rosemont during 2017, 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, 52 minutes later, at 8:33 PM, while on December 21, the shortest day of the year, it rises at 7:19 AM and sets 9 hours, 28 minutes later, at 4:47 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in April

The solar day over the course of April. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Humidity

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 Rosemont is essentially constant during April, remaining around 0% throughout.

For reference, on July 30, 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

The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

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 Rosemont is essentially constant during April, remaining within 0.1 miles per hour of 6.3 miles per hour throughout.

For reference, on July 20, the windiest day of the year, the daily average wind speed is 7.3 miles per hour, while on October 21, the calmest day of the year, the daily average wind speed is 5.3 miles per hour.

The lowest daily average wind speed during April is 6.3 miles per hour on April 20.

Average Wind Speed in April

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
The hourly average wind direction in Rosemont throughout April is predominantly from the south, with a peak proportion of 40% on April 4.

Wind Direction in April

Wind Direction in April in RosemontSW181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMaywestsouthnortheast
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Growing Season

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 Rosemont typically lasts for 10 months (314 days), from around January 29 to around December 9, rarely starting after March 1, or ending before November 16.

The month of April in Rosemont is reliably fully within the growing season.

Time Spent in Various Temperature Bands and the Growing Season in April

Time Spent in Various Temperature Bands and the Growing Season in April in Rosemontgrowing seasongrowing season181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMay98%Apr 198%Apr 1100%Apr 30100%Apr 3099%Apr 1199%Apr 11100%Apr 21100%Apr 21very coldcoldcoolcomfortablewarmhot
The percentage of time spent in various temperature bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The black line is the percentage chance that a given day is within the growing season.

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 Rosemont are increasing during April, increasing by 271°F, from 315°F to 586°F, over the course of the month.

Growing Degree Days in April

The average growing degree days accumulated over the course of April, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

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 Rosemont is increasing during April, rising by 1.4 kWh, from 5.4 kWh to 6.8 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in April

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Rosemont are 38.552 deg latitude, -121.365 deg longitude, and 52 ft elevation.

The topography within 2 miles of Rosemont is essentially flat, with a maximum elevation change of 66 feet and an average elevation above sea level of 51 feet. Within 10 miles is essentially flat (259 feet). Within 50 miles contains only modest variations in elevation (5,203 feet).

The area within 2 miles of Rosemont is covered by artificial surfaces (76%) and cropland (18%), within 10 miles by artificial surfaces (58%) and grassland (20%), and within 50 miles by cropland (36%) and grassland (28%).

Data Sources

This report illustrates the typical weather in Rosemont 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 Rosemont.

For each station, the records are corrected for the elevation difference between that station and Rosemont 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 Rosemont is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Rosemont and a given station.

The stations contributing to this reconstruction are: Sacramento Mather Airport (61%, 5.9 kilometers, east); Sacramento Executive Airport (21%, 12 kilometers, southwest); and Mc Clellan Airfield (19%, 13 kilometers, north).

Other Data

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.

Disclaimer

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.