St. Marys, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Marys, a city in Warren County, Iowa.
Overnight
45°F
Slight Chance Rain Showers
A slight chance of rain showers after 5am. Cloudy. Low around 45, with temperatures rising to around 47 overnight. West northwest wind 9 to 13 mph, with gusts as high as 20 mph. Chance of precipitation is 20%.
7-day forecast for St. Marys
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 45°F | Slight Chance Rain Showers | 9 to 13 mph WNW | 16% |
| Wednesday | 51°F | Slight Chance Rain Showers then Cloudy | 13 to 17 mph W | 17% |
| Wednesday Night | 44°F | Mostly Cloudy then Chance Rain Showers | 14 mph W | 27% |
| Thursday | 53°F | Chance Rain Showers then Cloudy | 13 mph NW | 30% |
| Thursday Night | 41°F | Mostly Cloudy | 7 to 10 mph NNW | 9% |
| Friday | 50°F | Partly Sunny | 5 to 8 mph N | 6% |
| Friday Night | 31°F | Partly Cloudy | 3 mph ENE | 0% |
| Saturday | 53°F | Mostly Sunny | 1 to 5 mph SW | 0% |
| Saturday Night | 37°F | Mostly Clear | 6 mph WSW | 1% |
| Sunday | 59°F | Sunny | 6 mph W | 1% |
| Sunday Night | 39°F | Clear | 6 mph SW | 0% |
| Monday | 65°F | Sunny | 6 to 10 mph SW | 0% |
| Monday Night | 42°F | Clear | 7 mph W | 0% |
| Tuesday | 64°F | Sunny | 5 mph NNW | 0% |
Forecast source: National Weather Service (api.weather.gov) for St. Marys (41.308, -93.734). Updated through the day.
Growing snapshot for St. Marys
Last spring frost
Apr 24
First fall frost
Oct 12
Growing season
168 days
Hardiness zone
5b
More local growing data for St. Marys: nearby ZIP 50241 weather · frost dates · planting calendar · Iowa frost dates
Nearby towns & communities
Ackworth
Carlisle
Hartford
Indianola
Lacona
Martensdale
Milo
New Virginia
Norwalk
Sandyville
Spring Hill
Climate data from the nearest NOAA station, Indianola 2W, Ia (6 mi from St. Marys). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.