Elgin straddles the Fox River, which periodically floods adjacent residential and commercial neighborhoods during spring snowmelt and heavy summer thunderstorm events. The area's clay-heavy glacial till soils have very low permeability, causing rapid surface water accumulation that overwhelms storm sewers during intense rainfall. Elgin averages 37 inches of annual precipitation, but severe summer convective storms can deliver 2–4 inches within hours, triggering widespread sump pump failures and basement flooding across the city's older housing stock.