Average Weather in April at Knox County Regional Airport Maine, United States
Daily high temperatures increase by 9°F, from 45°F to 54°F, rarely falling below 37°F or exceeding 64°F.
Daily low temperatures increase by 8°F, from 31°F to 39°F, rarely falling below 22°F or exceeding 46°F.
For reference, on July 26, the hottest day of the year, temperatures at Knox County Regional Airport typically range from 59°F to 74°F, while on January 29, the coldest day of the year, they range from 15°F to 31°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
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 month of April at Knox County Regional Airport experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 55% throughout the month.
The clearest day of the month is April 7, with clear, mostly clear, or partly cloudy conditions 46% of the time.
For reference, on May 16, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 57%, while on September 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.
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. At Knox County Regional Airport, the chance of a wet day over the course of April is essentially constant, remaining around 29% throughout.
For reference, the year's highest daily chance of a wet day is 32% on December 11, and its lowest chance is 21% on August 30.
Over the course of April at Knox County Regional Airport, the chance of a day with only rain increases from 23% to 27%, the chance of a day with mixed snow and rain decreases from 4% to 1%, and the chance of a day with only snow remains an essentially constant 1% throughout.
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 at Knox County Regional Airport is essentially constant, remaining about 3.5 inches throughout, and rarely exceeding 5.7 inches or falling below 1.2 inches.
The highest average 31-day accumulation is 3.6 inches on April 17.
Average Monthly Rainfall in April
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. As with rainfall, we consider the liquid-equivalent snowfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day liquid-equivalent snowfall during April at Knox County Regional Airport is gradually decreasing, starting the month at 0.4 inches, when it rarely exceeds 1.0 inches or falls below -0.0 inches, and ending the month at 0.1 inches, when it rarely exceeds 0.2 inches or falls below -0.0 inches.
Average Monthly Liquid-Equivalent Snowfall in April
Over the course of April at Knox County Regional Airport, 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, 53 seconds, and weekly increase of 20 minutes, 9 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 latest sunrise of the month at Knox County Regional Airport is 6:17 AM on April 1 and the earliest sunrise is 48 minutes earlier at 5:29 AM on April 30.
The earliest sunset is 7:03 PM on April 1 and the latest sunset is 35 minutes later at 7:38 PM on April 30.
Daylight saving time is observed at Knox County Regional Airport 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 4:53 AM and sets 15 hours, 30 minutes later, at 8:23 PM, while on December 21, the shortest day of the year, it rises at 7:08 AM and sets 8 hours, 53 minutes later, at 4:00 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 at Knox County Regional Airport is essentially constant during April, remaining around 0% throughout.
For reference, on August 2, the muggiest day of the year, there are muggy conditions 13% 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
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 at Knox County Regional Airport is decreasing during April, decreasing from 10.5 miles per hour to 8.6 miles per hour over the course of the month.
For reference, on January 31, the windiest day of the year, the daily average wind speed is 12.5 miles per hour, while on August 8, the calmest day of the year, the daily average wind speed is 6.3 miles per hour.
Average Wind Speed in April
Wind Direction in April
Knox County Regional Airport 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 at Knox County Regional Airport is increasing during April, rising by 4°F, from 38°F to 42°F, over the course of the month.
Average Water Temperature 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 at Knox County Regional Airport typically lasts for 5.4 months (167 days), from around May 1 to around October 15, rarely starting before April 16 or after May 16, and rarely ending before September 29 or after October 31.
The month of April at Knox County Regional Airport is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season rapidly increasing from 0% to 47% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in April
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
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 at Knox County Regional Airport are essentially constant during April, remaining within 12°F of 17°F throughout.
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 at Knox County Regional Airport is increasing during April, rising by 1.1 kWh, from 4.4 kWh to 5.5 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 Knox County Regional Airport are 44.061 deg latitude, -69.096 deg longitude, and 13 ft elevation.
The topography within 2 miles of Knox County Regional Airport contains only modest variations in elevation, with a maximum elevation change of 197 feet and an average elevation above sea level of 40 feet. Within 10 miles contains only modest variations in elevation (1,033 feet). Within 50 miles also contains very significant variations in elevation (1,532 feet).
The area within 2 miles of Knox County Regional Airport is covered by trees (49%), water (24%), and artificial surfaces (16%), within 10 miles by water (59%) and trees (34%), and within 50 miles by water (57%) and trees (39%).
This report illustrates the typical weather at Knox County Regional Airport 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
Knox County Regional Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.
In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.
The stations on which we may fall back include but are not limited to Wiscasset Airport, Waterville Robert Lafleur Airport, Augusta State Airport, Bangor International Airport, Hancock County-Bar Harbor Airport, Naval Air Station Brunswick, Auburn/Lewiston Municipal Airport, and Portland International Jetport.
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.