Ismay, MT Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Ismay, a town in Custer County, Montana.
Overnight
27°F
Mostly Clear
Mostly clear. Low around 27, with temperatures rising to around 29 overnight. Wind around 0 mph.
7-day forecast for Ismay
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 27°F | Mostly Clear | 0 mph | 0% |
| Wednesday | 53°F | Mostly Sunny | 0 to 7 mph NW | 0% |
| Wednesday Night | 29°F | Patchy Fog | 0 to 3 mph W | 0% |
| Thursday | 57°F | Patchy Fog then Mostly Sunny | 1 to 5 mph SSE | 0% |
| Thursday Night | 32°F | Partly Cloudy | 3 mph SW | 0% |
| Friday | 55°F | Mostly Sunny | 2 to 9 mph W | 0% |
| Friday Night | 36°F | Mostly Clear | 5 to 9 mph SW | 0% |
| Saturday | 58°F | Sunny | 5 to 12 mph W | 0% |
| Saturday Night | 34°F | Mostly Clear | 5 mph SSW | 0% |
| Sunday | 64°F | Mostly Sunny | 3 to 9 mph SSW | 0% |
| Sunday Night | 40°F | Partly Cloudy | 6 mph W | 1% |
| Monday | 59°F | Mostly Sunny | 3 to 7 mph W | 1% |
| Monday Night | 36°F | Partly Cloudy | 3 mph SW | 1% |
| Tuesday | 61°F | Mostly Sunny | 2 to 8 mph SSW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Ismay (46.500, -104.793). Updated through the day.
Growing snapshot for Ismay
Last spring frost
May 22
First fall frost
Sep 15
Growing season
117 days
Hardiness zone
4a
More local growing data for Ismay: nearby ZIP 59336 weather · frost dates · planting calendar · Montana frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Mizpah 4 Nnw, Mt (16.7 mi from Ismay). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.