Tom's Blog

Wednesday, July 18, 2012

Precipitation history of Madison

In my last post I published a graph of the Palmer Drought Index for southcentral Wisconsin. This index reflects precipitation but includes other factors as well.

The graph in the present post presents precipitation data only.

Although the average annual precipitation for Madison is around 30 inches it varies widely from year to year. In recent  years the highest total has been the 44 inches  in 2008 and the lowest have been the 21 inches in 1976 and the 23 inches in 1988. The average in the so-called drought year of 2005 was about 25 inches.

However, annual averages do not show the time in the year when a precipitation deficit may have occurred. In 2005, for instance, the dry period was in late summer, whereas this year it was in June, the time when prairie plants are making their most growth. Thus, this year's drought is more serious, even if the annual average (which we won't know for another six months) is higher.

Thanks to the Wisconsin State Climatology Office, and its director John Young, for providing all this historical data!


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