Romeoville/Lewis Univ Arpt weather by month
Averages and records for each calendar month at Romeoville/Lewis Univ Arpt, United States, from 1997 to 2026. The warmest month is July, averaging 29.0°C; the coolest is January at −0.3°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | −0.3°C | −8.5°C | 18.3°C7 January 2008 | −31.1°C16 January 2009 | 29 / 29 |
| February | 2.4°C | −6.9°C | 22.8°C25 February 2000 | −25.6°C11 February 2014 | 29 / 29 |
| March | 9.4°C | −1.0°C | 29.4°C21 March 2012 | −25.0°C4 March 2002 | 29 / 29 |
| April | 16.2°C | 4.6°C | 31.7°C18 April 2002 | −8.3°C7 April 2018 | 29 / 29 |
| May | 22.2°C | 10.4°C | 36.1°C15 May 2025 | −3.3°C3 May 2005 | 29 / 29 |
| June | 27.2°C | 15.8°C | 37.2°C28 June 2012 | 3.9°C1 June 2003 | 29 / 29 |
| July | 29.0°C | 18.3°C | 38.9°C24 July 2005 | 8.9°C2 July 2001 | 29 / 29 |
| August | 27.9°C | 17.4°C | 36.1°C1 August 2006 | 8.3°C31 August 2009 | 29 / 29 |
| September | 24.9°C | 13.4°C | 34.4°C8 September 2002 | 2.2°C24 September 2012 | 29 / 30 |
| October | 17.5°C | 6.7°C | 31.7°C4 October 2005 | −4.4°C25 October 2013 | 29 / 29 |
| November | 9.6°C | 0.3°C | 25.0°C8 November 2020 | −14.4°C22 November 2015 | 29 / 29 |
| December | 2.6°C | −5.4°C | 21.7°C3 December 2012 | −24.4°C18 December 2016 | 29 / 29 |
Years shows the number behind the average high, then the number holding a record for that month. They differ because a year contributes an average only when the month has at least 25 days of readings, while a single reading is enough to set a record. The average low is withheld on the same 25-day rule and is counted separately again; it is shown as a dash where the archive cannot support it. Across the twelve months here the averages rest on 29 to 29 years each.
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Climate at nearby stations
The closest stations with twelve months of archive of their own, nearest first.
Every figure on this page is computed from NOAA GHCN-Daily observations stored per station, per year, per month. Nothing is modelled, interpolated or estimated, and a month the archive never covered is left out rather than filled in. A station appears here only once all twelve months carry an average from at least 10 years. See how this is built.