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High Dew Points - July 20, 2002
Minnesota's latest round of sultry weather peaked on Saturday, July 20. During the evening hours on that date, three
west central Minnesota locations; Madison, Morris, and Olivia; reported dew point temperatures of 84 degrees.
Dew point readings of 84 degrees match the highest dew point temperature values that the State Climatology Office
can locate in a cursory examination of the digital data set. Our examination identified one other episode of such
extraordinary dew point values. A handful of southern Minnesota locations reported 84 degree dew points on July 29
and 30, 1999.
The dew point temperature at the Twin Cities International Airport on Saturday, July 20 topped out at 80 degrees
(8:00 pm and 10:00 pm). 80 degree dew points are rare in the Twin Cities historical record. Since 1945, there have
been only twenty hours of 80 degree dew points recorded. Ten of those twenty hours came in a ten hour period on July
12 and 13, 1995. Dew point temperatures of 80 degrees were reported for at least one hour in three of the last four
years. The highest dew point temperature ever recorded in the Twin Cities was 81 degrees at 11:00 am on July 30, 1999.
The heat index, a "feels like" measure which factors together temperature and dew point, reached 123 degrees at
Madison, MN at 7:00 pm on July 20. At that time, the air temperature was 95 degrees and the dew point temperature was 84.
A quick scan of the historical database reveals only one heat index value exceeding 123 degrees. An air temperature of
97 degrees teamed with an 84 degree dew point to create a heat index value of 125 degrees at the Red Wing airport
at 3:00 pm on July 30, 1999.
mcwg@soils.umn.edu |
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