Climatological Percent of Possible Sunshine by Month


Percent of Possible Sunshine is defined as the number of minutes of direct sunlight received (no blocking clouds) divided by the number of minutes between sunrise and sunset.

Sunshine minutes are recorded daily at NWS Grand Rapids using a sensor that measures light intensity. Meteorologists will add the appropriate number of minutes to the sensor's total if there is direct sunlight observed around sunrise or sunset.

This chart shows the most, average, and least percents of possible sunshine received on a monthly basis, using data from 1981 to 2010. On average, July is the sunniest month and December is the cloudiest month.

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