Average Weather in Hartland Wisconsin, United States

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3. Wisconsin
4. Waukesha County
5. Hartland

In Hartland, the summers are warm and wet; the winters are freezing, dry, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 14°F to 81°F and is rarely below -5°F or above 90°F.

The warm season lasts for 3.8 months, from May 26 to September 19, with an average daily high temperature above 70°F. The hottest day of the year is July 19, with an average high of 81°F and low of 62°F.

The cold season lasts for 3.2 months, from November 30 to March 5, with an average daily high temperature below 38°F. The coldest day of the year is January 29, with an average low of 14°F and high of 27°F.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

In Hartland, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in Hartland begins around June 10 and lasts for 4.4 months, ending around October 23. On August 26, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 67% of the time, and overcast or mostly cloudy 33% of the time.

The cloudier part of the year begins around October 23 and lasts for 7.6 months, ending around June 10. On February 6, the cloudiest day of the year, the sky is overcast or mostly cloudy 59% of the time, and clear, mostly clear, or partly cloudy 41% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Hartland varies throughout the year.

The wetter season lasts 6.2 months, from March 30 to October 5, with a greater than 25% chance of a given day being a wet day. The chance of a wet day peaks at 38% on June 10.

The drier season lasts 5.8 months, from October 5 to March 30. The smallest chance of a wet day is 12% on February 10.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation in Hartland changes throughout the year.

Rain alone is the most common for 9.8 months, from February 21 to December 15. The highest chance of a day with rain alone is 38% on June 10.

Snow alone is the most common for 2.2 months, from December 15 to February 21. The highest chance of a day with snow alone is 9% on January 18.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Hartland experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 11 months, from February 9 to January 6, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around June 15, with an average total accumulation of 3.8 inches.

The rainless period of the year lasts for 1.1 months, from January 6 to February 9. The least rain falls around January 22, with an average total accumulation of 0.4 inches.

Snowfall

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. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Hartland experiences some seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 5.2 months, from November 11 to April 16, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around December 27, with an average total liquid-equivalent accumulation of 0.5 inches.

The snowless period of the year lasts for 6.8 months, from April 16 to November 11. The least snow falls around July 31, with an average total liquid-equivalent accumulation of 0.0 inches.

The length of the day in Hartland varies significantly over the course of the year. In 2017, the shortest day is December 21, with 8 hours, 59 minutes of daylight; the longest day is June 21, with 15 hours, 23 minutes of daylight.

The earliest sunrise is at 5:13 AM on June 14, and the latest sunrise is 2 hours, 19 minutes later at 7:32 AM on November 4. The earliest sunset is at 4:18 PM on December 9, and the latest sunset is 4 hours, 19 minutes later at 8:37 PM on June 26.

Daylight saving time (DST) is observed in Hartland during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.

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.

Hartland experiences significant seasonal variation in the perceived humidity.

The muggier period of the year lasts for 3.5 months, from June 5 to September 20, during which time the comfort level is muggy, oppressive, or miserable at least 10% of the time. The muggiest day of the year is August 1, with muggy conditions 37% of the time.

The least muggy day of the year is February 10, when muggy conditions are essentially unheard of.

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 Hartland experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.6 months, from October 1 to May 20, with average wind speeds of more than 5.7 miles per hour. The windiest day of the year is January 15, with an average hourly wind speed of 7.0 miles per hour.

The calmer time of year lasts for 4.4 months, from May 20 to October 1. The calmest day of the year is August 3, with an average hourly wind speed of 4.4 miles per hour.

The predominant average hourly wind direction in Hartland varies throughout the year.

The wind is most often from the north for 1.5 months, from March 3 to April 18, with a peak percentage of 32% on March 8. The wind is most often from the south for 1.5 months, from May 14 to June 30 and for 1.8 months, from August 10 to October 4, with a peak percentage of 36% on September 6. The wind is most often from the west for 1.4 months, from June 30 to August 10 and for 5.0 months, from October 4 to March 3, with a peak percentage of 33% on July 19.

Hartland 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 water temperature experiences significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 2.6 months, from July 6 to September 24, with an average temperature above 63°F. The day of the year with the warmest water is August 14, with an average temperature of 70°F.

The time of year with cooler water lasts for 5.5 months, from December 4 to May 18, with an average temperature below 43°F. The day of the year with the coolest water is February 28, with an average temperature of 36°F.

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 experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.5 months, from May 5 to August 19, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest day of the year is July 1, with an average of 7.0 kWh.

The darker period of the year lasts for 3.4 months, from October 30 to February 12, with an average daily incident shortwave energy per square meter below 2.7 kWh. The darkest day of the year is December 22, with an average of 1.6 kWh.

For the purposes of this report, the geographical coordinates of Hartland are 43.105 deg latitude, -88.342 deg longitude, and 935 ft elevation.

The topography within 2 miles of Hartland contains only modest variations in elevation, with a maximum elevation change of 190 feet and an average elevation above sea level of 944 feet. Within 10 miles contains only modest variations in elevation (528 feet). Within 50 miles also contains significant variations in elevation (738 feet).

The area within 2 miles of Hartland is covered by artificial surfaces (51%), cropland (33%), and trees (11%), within 10 miles by cropland (51%) and artificial surfaces (25%), and within 50 miles by cropland (61%) and water (21%).

This report illustrates the typical weather in Hartland, 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 Hartland.

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

The stations contributing to this reconstruction are: Waukesha County Airport (73%, 11 kilometers, southeast); Watertown Municipal Airport (15%, 31 kilometers, west); and West Bend Municipal Airport (11%, 39 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.