As has been the case in recent months, Iowa saw many large variations in temperature.   The first six days of the month were much cooler than usual with temperatures falling to 20�� at Sibley and Spencer on the 3rd.    A lower May minimum temperature has been recorded only four times in the past 100 years (most recently in 2005).   The second six days of the month were unusually warm with the temperature soaring to 100�� at Jefferson on the 10th.   This was Iowa���s earliest triple digit temperature since April 22, 1980 and the first time that 100 has been reached during the month since May 15, 2001.   The heat was followed by another six days of below normal temperatures (13th-18th) with scattered freezes reported on the mornings of the 16th and 17th.   Another six day period of unusual warmth followed on the 19th through the 24th.   The alternating six day temperature cycle was cut short by one day with below normal temperatures from the 25th through the 29th with Elkader reporting a low of 35�� on the 27th.   Finally, the last two days of the month brought very warm weather with Spencer and Sheldon reaching 91�� on the 30th.  The month began with a very welcome period of mostly dry weather with a statewide average of only 0.21 inches of rain for the first ten days of the month.  This helped to finally end the flooding along the upper Des Moines River.  Spring planting, which was far behind the normal pace in April, managed to surge ahead of the typical progress in early May with 84% of the corn and 47% of the soybeans planted during the first two weeks of the month according to Iowa Agricultural Statistics.   Rain became increasingly frequent for the remainder of the month, particularly on the 24th-25th when an average of 1.63 inches fell over Iowa.   The initial round of heavy rainfall brushed northern Iowa and fell in the upper portions of the Des Moines River basin in southern Minnesota that lead to flooding beginning by the 22nd in the Estherville area.  Rainfall was especially heavy over south central Iowa where Osceola reported 10.86 inches for the month.   This was the second highest ever total for rainfall in the month of May among 80 years of records in Osceola with May 1996 reporting 11.65 inches of rain. Meanwhile, a small area of east central Iowa experienced a drier than normal May with only 2.17 inches of rain recorded at Manchester for their driest May since 1992.  Flooding during the 3rd week of the month moved down the Des Moines River basin.  For the most part the flooding was relatively minor, not causing a great deal of damage.

Flood in KOSSUTH, IOWA
From 23-MAY-11 06:45:00 to 31-MAY-11 23:59:00 (CST-6)
Location: BURT
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in EMMET, IOWA
From 22-MAY-11 13:45:00 to 31-MAY-11 23:59:00 (CST-6)
Location: HUNTINGTON
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in HUMBOLDT, IOWA
From 25-MAY-11 09:21:00 to 31-MAY-11 23:59:00 (CST-6)
Location: HUMBOLDT MUNI ARPT
Flood cause: Heavy Rain
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in WEBSTER, IOWA
From 26-MAY-11 06:55:00 to 31-MAY-11 23:59:00 (CST-6)
Location: LEHIGH
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in WAPELLO, IOWA
From 25-MAY-11 06:13:00 to 26-MAY-11 04:20:00 (CST-6)
Location: EDDYVILLE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in MARION, IOWA
From 25-MAY-11 06:13:00 to 26-MAY-11 04:20:00 (CST-6)
Location: BUSSEY
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in DECATUR, IOWA
From 25-MAY-11 15:17:00 to 27-MAY-11 06:15:00 (CST-6)
Location: GRAND RIVER
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in WARREN, IOWA
From 25-MAY-11 06:52:00 to 26-MAY-11 01:05:00 (CST-6)
Location: HARTFORD
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flood in WAYNE, IOWA
From 25-MAY-11 06:41:00 to 26-MAY-11 11:11:00 (CST-6)
Location: CONFIDENCE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Official NWS Observations