St. Marys, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Marys, a city in Warren County, Iowa.
Today
82°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Partly sunny. High near 82, with temperatures falling to around 80 in the afternoon. West southwest wind 5 to 9 mph. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for St. Marys
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 82°F | Chance Showers And Thunderstorms | 5 to 9 mph WSW | 47% |
| Tonight | 62°F | Chance Showers And Thunderstorms | 9 mph N | 51% |
| Sunday | 66°F | Chance Rain Showers then Slight Chance Showers And Thunderstorms | 12 mph NNE | 43% |
| Sunday Night | 56°F | Chance Showers And Thunderstorms then Showers And Thunderstorms Likely | 13 mph NE | 62% |
| Monday | 61°F | Rain Showers Likely | 13 mph NE | 62% |
| Monday Night | 52°F | Rain Showers Likely | 10 mph NE | 58% |
| Tuesday | 60°F | Partly Sunny | 9 mph NE | 13% |
| Tuesday Night | 47°F | Partly Cloudy | 3 to 7 mph ENE | 4% |
| Wednesday | 63°F | Sunny | 6 mph ENE | 2% |
| Wednesday Night | 52°F | Partly Cloudy | 3 mph E | 4% |
| Thursday | 66°F | Slight Chance Rain Showers | 5 mph ESE | 22% |
| Thursday Night | 56°F | Mostly Cloudy | 5 mph ESE | 9% |
| Friday | 67°F | Partly Sunny | 2 to 6 mph ESE | 11% |
| Friday Night | 57°F | Mostly Cloudy | 5 mph ESE | 9% |
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 Sep 19, 2026.