Wednesday was certainly a very muggy day in Iowa. Dew point temperatures (a measure of the amount of moisture in the atmosphere) soared around 80 degrees at a number of observing sites. This news item summarizes some IEM computed tidbits on the extreme dewpoints of 14 July 2010.

In Iowa, the primary weather observation sites are located at the airports. There are two classes of sensors used at these sites. One class is known as ASOS and are operated by the federal government. Another is known as AWOS and are maintained by the state. In general, the AWOS sites are located literally in the middle of crop fields and use a temperature/humidity sensor that struggles at extreme values. Unless noted, data presented below are for ASOS sites and are generally considered accurate and representative.

The following presents a summary of the maximum dewpoint observed at ASOS sites and the previous date of a 80+ degree dewpoint.

ID  NAME          MAX   LAST 80+     ALLTIME MAX      DATA SINCE
AMW Ames          81   23 Jun 2009   84-29 Jul 1999   1997
BRL Burlington    81   23 Jun 2009   82-29 Jul 1999   1973
DBQ Dubuque       80   20 Jul 2002   82-13 Jul 1995   1973
CID Cedar Rapids  80   23 Jul 2005   87-13 Jul 1995   1973
DVN Davenport     77   13 Jul 2004   83-29 Jul 1999   1997
DSM Des Moines    80    3 Aug 2004   84- 6 Sep 1998   1970
EST Esterville    78    3 Aug 2008   83-29 Jul 1999   1997
IOW Iowa City     80   18 Jun 2009   84-20 Aug 1998   1997
LWD Lamoni        80    3 Aug 2004   80               1998
MIW Marshalltown  81    3 Aug 2008   83-29 Jul 1999   1997 
MCW Mason City    81   25 Jul 2005   83-29 Jul 1999   1961
OTM Ottumwa       81    3 Aug 2004   82-18 Jul 1996   1973
SPW Spencer       79    6 Aug 2001   82-29 Jul 1999   1973
ALO Waterloo      82    8 Aug 2009   83-29 Jul 1999   1970
SUX Sioux City    80   23 Jun 2009   83-22 Jul 2005   1961

So 12 ASOS sites hit 80+ today, this is rather unprecidented. One has to go back to 23 July 2005 to find widespread observations of 80+ dew points. 29 July 1999 is the most recent comparable day to today.

For AWOS sites, Newton reported a dew point of 88, Fairfield 86, Knoxville 85, Vinton 85, and Orange City 85.