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Average Weather in April in Ontario Oregon, United States

Daily high temperatures increase by 9°F, from 61°F to 70°F, rarely falling below 51°F or exceeding 83°F.

Daily low temperatures increase by 6°F, from 37°F to 43°F, rarely falling below 28°F or exceeding 52°F.

For reference, on July 26, the hottest day of the year, temperatures in Ontario typically range from 62°F to 93°F, while on January 1, the coldest day of the year, they range from 22°F to 34°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 Ontario1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM4 AM8 AM12 PM4 PM8 PM12 AMMarMayvery coldvery coldcoldcoolcoolcomfortable
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.

Gorobinci, Macedonia (5,984 miles away); Arguvan, Turkey (6,518 miles); and Pasragad Branch, Iran (6,923 miles) are the far-away foreign places with temperatures most similar to Ontario (view comparison).


The month of April in Ontario experiences gradually decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 53% to 48%.

The clearest day of the month is April 30, with clear, mostly clear, or partly cloudy conditions 52% of the time.

For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 60%, while on July 28, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 84%.

Cloud Cover Categories in April

Cloud Cover Categories in April in Ontario181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMayApr 147%Apr 147%Apr 3052%Apr 3052%Apr 1148%Apr 1148%Apr 2150%Apr 2150%clearmostly clearpartly cloudymostly cloudyovercast
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.


A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Ontario, the chance of a wet day over the course of April is essentially constant, remaining around 15% throughout.

For reference, the year's highest daily chance of a wet day is 24% on December 1, and its lowest chance is 3% on July 29.

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).


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 Ontario is essentially constant, remaining about 0.7 inches throughout, and rarely exceeding 1.5 inches or falling below 0.1 inches.

The lowest average 31-day accumulation is 0.7 inches on April 15.

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.


Over the course of April in Ontario, 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, 23 minutes, implying an average daily increase of 2 minutes, 52 seconds, and weekly increase of 20 minutes, 7 seconds.

The shortest day of the month is April 1, with 12 hours, 46 minutes of daylight and the longest day is April 30, with 14 hours, 9 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 Ontario is 7:28 AM on April 1 and the earliest sunrise is 48 minutes earlier at 6:40 AM on April 30.

The earliest sunset is 8:15 PM on April 1 and the latest sunset is 35 minutes later at 8:50 PM on April 30.

Daylight saving time is observed in Ontario 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 6:04 AM and sets 15 hours, 29 minutes later, at 9:34 PM, while on December 21, the shortest day of the year, it rises at 8:19 AM and sets 8 hours, 53 minutes later, at 5:12 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.


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

For reference, on August 3, the muggiest day of the year, there are muggy conditions 0% of the time, while on September 23, 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.


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 Ontario is essentially constant during April, remaining within 0.1 miles per hour of 7.2 miles per hour throughout.

For reference, on April 11, the windiest day of the year, the daily average wind speed is 7.3 miles per hour, while on January 10, the calmest day of the year, the daily average wind speed is 5.6 miles per hour.

The highest daily average wind speed during April is 7.3 miles per hour on April 11.

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 Ontario throughout April is predominantly from the north, with a peak proportion of 43% on April 30.

Wind Direction in April

Wind Direction in April in Ontario181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMaywestsoutheastnorth
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 Ontario typically lasts for 5.6 months (170 days), from around April 26 to around October 13, rarely starting before April 4 or after May 16, and rarely ending before September 24 or after November 1.

During April in Ontario, the chance that a given day is within the growing season is very rapidly increasing rising from 7% to 61% over the course of the month.

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 Ontario181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%MarMayApr 17%Apr 17%61%Apr 3061%Apr 30Apr 1119%Apr 1119%Apr 2138%Apr 2138%90%May 1690%May 16freezingvery coldcoldcoolcomfortablewarm
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 Ontario are gradually increasing during April, increasing by 147°F, from 66°F to 213°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 Ontario is increasing during April, rising by 1.4 kWh, from 5.0 kWh to 6.4 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.


For the purposes of this report, the geographical coordinates of Ontario are 44.027 deg latitude, -116.963 deg longitude, and 2,156 ft elevation.

The topography within 2 miles of Ontario is essentially flat, with a maximum elevation change of 82 feet and an average elevation above sea level of 2,159 feet. Within 10 miles is essentially flat (945 feet). Within 50 miles contains very significant variations in elevation (6,135 feet).

The area within 2 miles of Ontario is covered by artificial surfaces (50%), cropland (26%), and shrubs (23%), within 10 miles by cropland (65%) and grassland (19%), and within 50 miles by shrubs (55%) and grassland (20%).

Data Sources

This report illustrates the typical weather in Ontario 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 Ontario.

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

The stations contributing to this reconstruction are: Ontario Municipal Airport (97%, 4.1 kilometers, west); Caldwell Industrial Airport (2.3%, 50 kilometers, southeast); and McCall Airport (0.5%, 118 kilometers, northeast).

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.


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.