O'Fallon, MO Weather Records Since April 2005
| Temperature | ||
| Highest Temperature | 103.1 °F | at 4:00 PM on 15 August 2007 |
| Highest Heat Index | 124.1 °F | at 6:28 PM on 02 August 2011 |
| Lowest Temperature | -2.6 °F | at 6:36 AM on 10 January 2010 |
| Lowest Windchill | -17.2 °F | at 8:15 AM on 09 January 2010 |
| Highest Minimum | 81.5 °F | at 4:52 AM on 11 July 2011 |
| Lowest Maximum | 15.5 °F | at 12:00 AM on 21 January 2011 |
| Rainfall | ||
| Highest Rain Rate | 18.00 in/hr | at 12:40 PM on 13 July 2010 |
| Highest Hourly Rain | 1.67 in | at 12:01 AM on 26 June 2011 |
| Highest Daily Rain | 5.93 in | on 15 October 2005 |
| Highest Monthly Rain | 12.03 in | October 2009 |
| Wind | ||
| Highest Gust | 56.0 mph | at 6:30 PM on 13 June 2010 |
| Highest Average | 24.0 mph | at 4:32 PM on 03 July 2011 |
| Pressure | ||
| Highest Pressure | 30.695 in | at 9:52 PM on 12 January 2011 |
| Lowest Pressure | 29.027 in | at 3:30 AM on 26 October 2010 |
| Page Updated | 2/22/2012 2:55:01 PM |