Wisconsin State Climatology Office

SEASONAL VARIATIONS IN HOURLY AIR TEMPERATURE

The accompanying image is a plot of the variations in the hourly temperatures observed at the weather station throughout the year.  The average temperature for each hour of the day at the station was computed from the set of observed hourly temperatures 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).   Isotherms (lines of equal temperature) were computer generated and displayed using a krieging technique.

INTERPRETATION:

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

Moving vertically along any day, the highest hourly temperature usually is found in early afternoon (centered at approximately 1400 or 2 PM CST), while the lowest temperatures typically occur just before sunrise. Since the sunrise varies throughout the year, the occurrence of these lowest hourly temperatures appearing on these analyzed plots also reflect these seasonal variations.   For example, the lowest hourly temperatures in mid winter occur at about 0600-0700 CST (6-7 AM), while in summer, the lowest hourly temperatures are at about 0500 (5 AM) CST.

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


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Latest revision: 24 April 2004

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