The difference in dew point temperature from the air temperature is called the dew point depression. On Wednesday, the dew point depressions in Iowa were over 50 degrees Fahrenheit for some locations with a air temperature in the 90s and dew point in the 40s. For Iowa, this is a very rare event! The featured chart presents the largest dew point depression by year and the minimum dew point observed with an air temperature at or above 95 for Des Moines. The bottom chart shows that having such a low dew point and high temperature is very rare and last happened in 1955 (red bars). The upper chart shows that having a 50+ degree spread has happened in a number of past years, but for August it last happened in 1936 (not shown)!

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Tags:   2012   dewpoint