Listener Question: Days Of Rain |
 Dave Thurlow, Host |
Hi, I'm Dave Thurlow from New Hampshires Mount Washington Observatory and this is The Weather Notebook. Today's listener question/comment is about rainfall averages and how they don't tell a complete story. Here's Bob Harmon from Bloomington, Indiana where he listens to WFIU:
Bob: "We get about 3 inches of rain a year in the month of May and several years ago we had a very long dry spell. The whole month of May was dry, less than a tenth of an inch. Except on the 2nd of May when we had 2 very heavy thunderstorms, over 4 inches. It all came on one day. So, If you look in the record book, it looks a little wet compared to the average. If you ask the farmers, it was very dry, almost the start of a drought. So, the question then becomes, do we have a frequency or distribution index?"
Ya we do. It's called number of days with per month. It's something that all weather observers count and report at the end of every month. In your case Bob, the number of days with rain was two, so with that information you know there was above average rainfall but most of just ran off into streams and rivers instead of soaking into the ground like the same monthly total would have if the month had say, 25 days with rain.
Now statistics like number of day per month with rain are collected by your state climatologist. Yes there is such a person. For a list of all of the state climatologists, please check weathernotebook.org. If you have a weather question like Bob did please cal 1-888rain001, and leave it on our machine. The Weather Notebook is produced by the Mount Washington Observatory, with support from Subaru -- the beauty of All-Wheel Drive and The National Science Foundation.