For those without snowcover, temperatures warmed very nicely over the weekend into the 40s and even briefly the 50s for a lucky few. Those with out snow were likely crediting the clear skies for allowing sunshine to warm us up, but the impact of clear skies on temperature is not straight forward this time of year. The featured chart presents the temperature difference between when skies were reported clear versus the period of record observations by week of the year and local hour of the day. The chart shows that having sunshine has the largest warming during the warmer half of the season. This is due to more direct insolation during periods closer to the summer than winter. During the winter time, things like snow cover and which air mass is currently visiting the state are more important to determine our temperatures. The chart also nicely shows that the impact during the night time hours is almost always negative (cooler) as the absence of clouds allow long wave terrestrial radiation to escape.

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Tags:   clouds