It’s May: Time for a Rainfall Update!

It’s almost the end of May and the spring rainy season… Time for our annual update on spring showers and local rainfall trends!

May 2018 Rainstorm

As far as I know, Wilmette’s first big downpour came late in the season this year, on May 21, 2018. Village staff have reported that rainfall lasted from 7AM to 2PM (7 hours), registering approximately 2 inches at the westside Storm Water Pump Station (a 1.5-yr storm) and 1.5 inches at the eastside Water Treatment Plant (a 6-month storm). The most intense portion was from around 10:30 AM to 11:30 AM, totaling 1 inch on the westside and .7 inch on the eastside.

As expected, the storm sewers on my street started backing up around 11:15 AM (shown above). Surcharging started at around a 1.5- or 2-year-storm level of intensity. Luckily, the worst rainfall ended within the hour, and the storm sewers cleared quickly.

Rainfalls of Record

While hunting for updated rainfall data, I secured some more information from the Village of Wilmette Water Plant. Staff provided a PDF table, listing Rainfall Storms of record for 1980-2017:


Note that the village measures rainfall using rain gauges at two locations:

  • Eastside Wilmette: Water Treatment Plant (WTP)
  • Westside Wilmette: Storm Water Pump Station (SWPS)

I converted the Water Department table into an Excel spreadsheet, added the preliminary May 21 storm stats, and sorted chronologically, to create this spreadsheet of 1980-2018 Storms of Record:



I’ll try to add more rainfall data as it becomes available. Any thoughts on trends/issues?

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