Windy

Last week I asked a couple people why it's less windy in the summer than at other times, and they gave me the same look they would have if I'd asked why marshmallows are harder than rocks. Well, folks, it really is less windy in the summer (and, to my surprise, in early fall) than at other times.

NOAA publishes data on average monthly wind speed for 270 weather stations in the United States. On average, there are 39 years of data for each station. In June, 70 percent of the stations report wind speeds below the annual average, and in July, 81 percent of the stations report below average winds. The percentage continues to climb through September and then falls off only a little in October. Graphically:
So, below average winds are typical in the U.S. for June-October. How much below average? For each station, let's find the difference between the wind speed each month and the average annual windspeed at that station. Calculating the average difference across all stations gives us this picture:

August shows the largest difference between monthly average and annual average wind speeds, about 1.3 MPH.

So I'm vindicated. Winds really are calmer in the "summer" months. What surprises me is how small the difference is between summer winds and annual average wind.