Ismay, MT Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Ismay, a town in Custer County, Montana.
Tonight
57°F
Chance Showers And Thunderstorms
A slight chance of showers and thunderstorms between 10pm and 11pm, then a chance of showers and thunderstorms between 11pm and midnight, then a chance of showers and thunderstorms between midnight and 3am, then patchy fog and a chance of showers and thunderstorms. Mostly cloudy. Low around 57, with temperatures rising to around 59 overnight. East wind 2 to 6 mph. Chance of precipitation is 50%.
7-day forecast for Ismay
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 57°F | Chance Showers And Thunderstorms | 2 to 6 mph E | 46% |
| Saturday | 66°F | Patchy Fog | 3 to 12 mph E | 88% |
| Saturday Night | 53°F | Rain Showers | 8 to 12 mph E | 86% |
| Sunday | 63°F | Rain Showers | 9 to 13 mph ESE | 89% |
| Sunday Night | 50°F | Slight Chance Rain Showers then Mostly Cloudy | 5 to 12 mph ESE | 15% |
| Monday | 70°F | Partly Sunny | 5 to 12 mph SE | 6% |
| Monday Night | 51°F | Partly Cloudy | 9 to 14 mph SE | 1% |
| Tuesday | 78°F | Sunny | 8 to 12 mph SSE | 0% |
| Tuesday Night | 53°F | Mostly Clear | 5 to 12 mph SSE | 3% |
| Wednesday | 81°F | Mostly Sunny | 6 mph SSE | 13% |
| Wednesday Night | 54°F | Mostly Clear | 3 mph SSE | 10% |
| Thursday | 82°F | Sunny | 2 to 7 mph SSE | 3% |
| Thursday Night | 55°F | Mostly Clear | 5 to 8 mph SE | 4% |
| Friday | 82°F | Mostly Sunny | 6 to 12 mph SE | 1% |
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 Sep 19, 2026.