Wisconsin State Climatology Office


The accompanying image is a plot of the variations in the hourly dewpoint temperatures (or dewpoint for short) observed at the weather station throughout the year.  The average dewpoint for each hour of the day at the station was computed from the set of observed hourly dewpoints for the given station for the 30 years from 1971-2000. 

The horizontal axis displays the day of the year, while the vertical axis represents the hour of the day (in the 24-hour format and in Central Standard Time).   Lines of equal dewpoints (also know as isodrostherms) were computer generated and displayed using a krieging technique.


By selecting any hour of the day and moving horizontally, the seasonal variations in that hour's dewpoint can be seen.  The lowest dewpoints typically occur in the mid winter (days 1-50 = Jan-Feb) when the air temperatures are also low, while the highest dewpoints are found in mid summer (days 180-210= July) when the air is warm. 

Some small daily variations in the dewpoint are apparent, especially during the summer.   Move vertically along any day, keeping parallel to the vertical axis.  Slightly higher hourly dewpoints typically are found during the afternoon and evening (centered at approximately 1800 or 6 PM CST), while the lower dewpoints are found during the night.

Prepared by Edward J. Hopkins, Ph.D., Assistant State Climatologist

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Latest revision: 25 April 2004

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URL Address: http://www.aos.wisc.edu/~sco/stations/ann_hrly_dewpt.html