Being now one day removed from the longest day of the year, it makes sense that another day with mostly clear skies was able to support warm daytime temperatures thanks to ample heating. The effect of having clear skies on temperatures is featured with today's chart. The chart compares hourly temperatures by week of the year for Des Moines between the case of having clear skies reported against all other reports. Yes, there are some caveats with how an automated station can report clear skies, but the chart nicely shows the intuitive relationship and some neat annual quirks. The red areas of the chart indicate that air temperatures are, on average, warmer during clear skies than not and green vice versa. The impact of daytime heating of the sun is immediately obvious, but you may notice the opposite impact during the winter months. Clouds during the winter months are typically a positive for temperatures as heat from the surface is absorbed and re-transmitted back to the ground helping to buoy temperatures. There's also a very nice negative influence on temperature just before sunrise as again the absence of clouds during the overnight hours allow temperatures to cool with the peak accumulated cooling happening just before sunrise.

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