Waterloo, IL Weather & Growing Conditions
Today
86°F
Patchy Fog then Sunny
Patchy fog before 7am. Sunny, with a high near 86. Southeast wind around 2 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 86°F | Patchy Fog then Sunny | 2 mph SE | 0% |
| Tonight | 66°F | Mostly Clear | 3 mph SE | 0% |
| Wednesday | 89°F | Sunny | 5 mph S | 5% |
| Wednesday Night | 70°F | Partly Cloudy then Chance Showers And Thunderstorms | 6 mph S | 53% |
| Thursday | 86°F | Chance Showers And Thunderstorms then Showers And Thunderstorms Likely | 5 mph S | 65% |
| Thursday Night | 69°F | Chance Showers And Thunderstorms | 3 mph S | 49% |
| Friday | 86°F | Chance Showers And Thunderstorms | 3 mph SW | 49% |
| Friday Night | 69°F | Chance Showers And Thunderstorms | 2 mph S | 40% |
| Saturday | 88°F | Chance Showers And Thunderstorms | 3 mph S | 40% |
| Saturday Night | 71°F | Mostly Clear | 5 mph S | 10% |
| Sunday | 90°F | Sunny | 6 mph S | 8% |
| Sunday Night | 72°F | Mostly Clear | 7 mph S | 5% |
| Monday | 92°F | Sunny | 7 mph SW | 5% |
| Monday Night | 73°F | Mostly Clear | 7 mph SW | 11% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Waterloo, IL
Last spring frost
Apr 9
First fall frost
Oct 26
Growing season
197 days
Hardiness zone
7a
Explore more for Waterloo, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Festus, Mo (14.5 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.