Posted by: JeffMasters, 2:53 PM GMT on March 21, 2012
Summer in March continued for the eighth day yesterday, toppling dozens of records for hottest March day in both the U.S. and Canada. Nearly every major airport in Michigan's Lower Peninsula tied or set records for their hottest March temperature, including Detroit (82°), Flint (84°F), Saginaw (83°F), Grand Rapids (83°), Muskegon (82°), Lansing (83°), Alpena (84°), Gaylord (80°), Pellston (84°), Traverse City (86°), and Houghton Lake (81°). Most of these records will be broken again today or tomorrow. Detroit's current string of six days over 70° is unprecedented so early in the year. One has to go back over 125 years to find an early-season warm spell that compares, and even that streak occurred in April, a full month later (April 16 - 24, 1886.)
How rare is this Summer in March heat event?
One measure of how record-breaking this "Summer in March" heat wave has been is the impact it had on NOAA's National Climatic Data Center web site. The extremes section of the their web site has been down since last Friday, since their software has been unable to handle both the huge number of records being set and the huge demand from people wanting to see these records. The web site came back on-line this morning with software re-engineered to handle the load, but only with data through Sunday.
We can also quantify how rare a meteorological event is by looking at statistics of past years. By averaging together at least 30 years of data to take a representative snapshot of the climate, we can generate a mean and a standard deviation of the data. The standard deviation gives a measure of how much the data fluctuates around the mean.
In comparing deviations from normal across wide regions, it helps to normalize the deviations. A temperature deviation of 3 degrees C may be not that unusual in one region, but may be very significant in another.
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