Average Weather in Fort Atkinson Wisconsin, United States

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5. Fort Atkinson

In Fort Atkinson, the summers are long, 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 83°F and is rarely below -6°F or above 90°F.

The warm season lasts for 3.9 months, from May 22 to September 19, with an average daily high temperature above 71°F. The hottest day of the year is July 19, with an average high of 83°F and low of 63°F.

The cold season lasts for 3.2 months, from November 30 to March 4, with an average daily high temperature below 39°F. The coldest day of the year is January 29, with an average low of 14°F and high of 28°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 Fort Atkinson, 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 Fort Atkinson begins around June 8 and lasts for 4.5 months, ending around October 25. 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 25 and lasts for 7.4 months, ending around June 8. On January 2, 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 Fort Atkinson varies throughout the year.

The wetter season lasts 6.1 months, from March 31 to October 4, with a greater than 26% 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 5.9 months, from October 4 to March 31. The smallest chance of a wet day is 13% on February 11.

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 Fort Atkinson changes throughout the year.

Rain alone is the most common for 10 months, from February 11 to December 20. The highest chance of a day with rain alone is 38% on June 10.

Snow alone is the most common for 1.7 months, from December 20 to February 11. 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. Fort Atkinson experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 11 months, from February 2 to January 8, 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 4.1 inches.

The rainless period of the year lasts for 3.6 weeks, from January 8 to February 2. The least rain falls around January 21, 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. Fort Atkinson experiences some seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 4.9 months, from November 11 to April 7, 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 7.1 months, from April 7 to November 11. The least snow falls around August 1, with an average total liquid-equivalent accumulation of 0.0 inches.

The length of the day in Fort Atkinson varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 1 minute of daylight; the longest day is June 21, with 15 hours, 21 minutes of daylight.

The earliest sunrise is at 5:15 AM on June 14, and the latest sunrise is 2 hours, 18 minutes later at 7:33 AM on November 4. The earliest sunset is at 4:20 PM on December 7, and the latest sunset is 4 hours, 18 minutes later at 8:38 PM on June 26.

Daylight saving time (DST) is observed in Fort Atkinson 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.

Fort Atkinson experiences significant seasonal variation in the perceived humidity.

The muggier period of the year lasts for 3.5 months, from June 3 to September 18, during which time the comfort level is muggy, oppressive, or miserable at least 11% of the time. The muggiest day of the year is July 22, with muggy conditions 43% of the time.

The least muggy day of the year is December 9, 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 Fort Atkinson experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.7 months, from October 2 to May 25, with average wind speeds of more than 5.6 miles per hour. The windiest day of the year is March 24, with an average hourly wind speed of 6.8 miles per hour.

The calmer time of year lasts for 4.3 months, from May 25 to October 2. The calmest day of the year is August 3, with an average hourly wind speed of 4.3 miles per hour.

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

The wind is most often from the east for 1.3 months, from April 5 to May 15, with a peak percentage of 29% on April 26. The wind is most often from the south for 1.6 months, from May 15 to July 2 and for 2.1 months, from August 7 to October 9, with a peak percentage of 37% on September 6. The wind is most often from the west for 1.2 months, from July 2 to August 7 and for 4.7 months, from October 9 to February 28, with a peak percentage of 33% on July 13.

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 Fort Atkinson are 42.929 deg latitude, -88.837 deg longitude, and 804 ft elevation.

The topography within 2 miles of Fort Atkinson contains only modest variations in elevation, with a maximum elevation change of 144 feet and an average elevation above sea level of 802 feet. Within 10 miles also contains only modest variations in elevation (276 feet). Within 50 miles contains only modest variations in elevation (906 feet).

The area within 2 miles of Fort Atkinson is covered by cropland (55%) and artificial surfaces (33%), within 10 miles by cropland (78%), and within 50 miles by cropland (76%) and artificial surfaces (10%).

This report illustrates the typical weather in Fort Atkinson, 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Fort Atkinson.

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

The stations contributing to this reconstruction are: Watertown Municipal Airport (40%, 28 kilometers, north); Southern Wisconsin Regional Airport (25%, 38 kilometers, southwest); Dane County Regional Airport (18%, 48 kilometers, northwest); and Burlington Municipal Airport (16%, 51 kilometers, southeast).

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.