Cooling degree days are a broad measure of how much air conditioning will be needed. To calculate the heating degree days for a particular day, find the day's average temperature by adding the day's high and low temperatures and dividing by two. If the number is above 65, there are no heating degree days that day. If the number is less than 65, subtract it from 65 to find the number of heating degree days. They’re essentially a departure from 65 degrees.
At Dulles Airport, for example, on Saturday August 17th the high was 80 and the low was 55, meaning the average temperature was 68. 68 minus 65 meant there were 3 cooling degree days on Saturday. The past week started warm, and there were 14 degree days on Monday and 13 on Tuesday but the rest of the week was cool and there were only six cooling degree days through Saturday. For the month, we’ve had 146 to date, but the normal is 188 and last year was 245 so this is just another measure of how cool we’ve been.
My rain gauge in Lorton recorded 0.35” of rain last week.
