Waterloo, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Waterloo, a city in Monroe County, Illinois.
Overnight
71°F
Partly Cloudy
Partly cloudy, with a low around 71. South wind around 6 mph.
7-day forecast for Waterloo
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 71°F | Partly Cloudy | 6 mph S | 6% |
| Saturday | 97°F | Mostly Sunny | 3 to 7 mph SW | 6% |
| Saturday Night | 72°F | Partly Cloudy | 5 mph SW | 0% |
| Sunday | 93°F | Mostly Sunny | 6 mph W | 14% |
| Sunday Night | 67°F | Chance Showers And Thunderstorms | 6 mph N | 52% |
| Monday | 81°F | Showers And Thunderstorms Likely | 5 to 9 mph N | 65% |
| Monday Night | 60°F | Showers And Thunderstorms Likely then Slight Chance Showers And Thunderstorms | 6 to 9 mph N | 65% |
| Tuesday | 71°F | Slight Chance Rain Showers then Mostly Cloudy | 10 mph N | 21% |
| Tuesday Night | 54°F | Mostly Cloudy | 5 to 9 mph N | 7% |
| Wednesday | 74°F | Mostly Sunny | 7 mph N | 2% |
| Wednesday Night | 54°F | Partly Cloudy | 6 mph N | 2% |
| Thursday | 74°F | Mostly Sunny | 3 to 7 mph N | 3% |
| Thursday Night | 57°F | Partly Cloudy | 6 mph N | 3% |
| Friday | 75°F | Mostly Sunny | 3 to 7 mph N | 5% |
Forecast source: National Weather Service (api.weather.gov) for Waterloo (38.341, -90.153). Updated through the day.
Growing snapshot for Waterloo
Last spring frost
Apr 9
First fall frost
Oct 26
Growing season
197 days
Hardiness zone
7a
More local growing data for Waterloo: nearby ZIP 62298 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Festus, Mo (14.5 mi from Waterloo). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.