Iowa Annual Rainfall and Climate Data, see below for individual cities 

 Iowa Average Annual Precipitation

Iowa city precipitation totals

City

Avg Annual Precip

Avg Annual Snow

 Avg # days of Precip

Avg # snow days

Avg # thunderstorm days

Avg # hail days

Avg # severe thunderstorm watches per year

Avg # tornado watches per year

 # of tornadoes reported in county, 1960-2010
Des Moines 34.72 31.8 108 64 46 2 7 16 47
Dubuque 35.52 42.1 117 62 35 2 6 14 20
Sioux City 25.99 32.0 99 63 43 2 7 15 47
Waterloo 33.15 31.8 103 63 41 1 7 14 33
  • Iowa Annual Precipitation Average - 34.05 inches, 31st wettest state in the U.S.
  • Iowa Tornado Average -  31.2 per year -  6th most in the U.S. 
  • Largest reported Tornado in Iowa from 1950-2011, 4/9/2011 - 2,640 yards / 1.5 miles wide
  • Date with highest number of reported Tornadoes in Iowa from 1950-2011, June 7th - 58 tornadoes
  • Average time of occurrence of reported Tornadoes in Iowa from 1950-2011 - 2:34 pm
  • Iowa Annual Lightning Density - 11.4 flashes per square mile - 14th highest in U.S. 
  • Record Driest year in Iowa from 1895-2012 - 1910, avg precipitation 10.87 inches 
  • Record Wettest year in Iowa from 1895-2012 - 1993, avg precipitation 48.23 inches  

Iowa Precipitation Records

  • Driest location ranked by lowest annual average precipitation: Akron, northwest Iowa, 25.81"
  • Wettest location ranked by highest annual average precipitation: Lamoni, southern Iowa, 39.37"
  • Snowiest location ranked by highest annual average snowfall: Dubuque, eastern Iowa, 43.8"
  • State precipitation maximum for 24 hours - Decatur county, southern Iowa, 8/5-6/1959, 16.70" 
  • State precipitation maximum for 1 year - Muskatine, southeast Iowa, 1851, 74.50"
  • State snow maximum for 24 hours - Sibley, northwest Iowa, 2/18/1962, 21.0"
  • State snow maximum for 1 season - Northwood, northern Iowa, 1908-1909, 90.4"
  • On May 28, 1942, the latest snowstorm of record for the state of Iowa left 10 inches at LeMars,
    8 inches at Cherokee, and 7.5 inches at Waukon. Afternoon highs were in the lower 30s in parts of
    northwetstern Iowa
  • On July 14, 1987, severe thunderstorms in Iowa produced eight inches of golf ball size hail near
    Grafton, Iowa, completely stripping corn stalks in the area.

Data sources: National Climatic Data Center, severe thunderstorm / tornado watch data period is 1999 - 2008, NOAA Storm Prediction Center
Tornado climate data - NOAA Storm Prediction Center, State lightning flash density average - 1997-2011, Vaisala