Defiance, MO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Defiance, a community in St. Charles County, Missouri.
This Afternoon
97°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Sunny, with a high near 97. Heat index values as high as 109. Southwest wind around 1 mph. Chance of precipitation is 30%.
7-day forecast for Defiance
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 97°F | Chance Showers And Thunderstorms | 1 mph SW | 26% |
| Tonight | 72°F | Slight Chance Showers And Thunderstorms then Mostly Clear | 1 mph SE | 21% |
| Saturday | 97°F | Mostly Sunny | 2 to 6 mph SW | 5% |
| Saturday Night | 71°F | Partly Cloudy | 2 mph S | 3% |
| Sunday | 92°F | Chance Rain Showers then Chance Showers And Thunderstorms | 3 mph W | 25% |
| Sunday Night | 66°F | Chance Showers And Thunderstorms then Showers And Thunderstorms Likely | 3 mph N | 64% |
| Monday | 79°F | Showers And Thunderstorms Likely | 6 mph N | 69% |
| Monday Night | 59°F | Showers And Thunderstorms Likely then Slight Chance Showers And Thunderstorms | 7 mph N | 69% |
| Tuesday | 71°F | Slight Chance Rain Showers then Mostly Cloudy | 7 mph N | 24% |
| Tuesday Night | 53°F | Mostly Cloudy | 2 to 6 mph N | 6% |
| Wednesday | 74°F | Mostly Sunny | 5 mph N | 1% |
| Wednesday Night | 54°F | Partly Cloudy | 3 mph N | 0% |
| Thursday | 75°F | Mostly Sunny | 3 mph N | 3% |
| Thursday Night | 57°F | Partly Cloudy | 2 mph NE | 3% |
Forecast source: National Weather Service (api.weather.gov) for Defiance (38.633, -90.785). Updated through the day.
Growing snapshot for Defiance
Last spring frost
Apr 10
First fall frost
Oct 26
Growing season
199 days
Hardiness zone
6b
More local growing data for Defiance: nearby ZIP 63341 weather · frost dates · planting calendar · Missouri frost dates
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West Alton
Climate data from the nearest NOAA station, Weldon Spring Nws, Mo (7.2 mi from Defiance). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.