Keystone, SD Weather & Growing Conditions
This Afternoon
74°F
Slight Chance Showers And Thunderstorms
A slight chance of rain showers before 4pm, then a slight chance of showers and thunderstorms. Mostly sunny. High near 74, with temperatures falling to around 70 in the afternoon. East wind around 5 mph, with gusts as high as 16 mph. Chance of precipitation is 20%.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 74°F | Slight Chance Showers And Thunderstorms | 5 mph E | 17% |
| Tonight | 57°F | Showers And Thunderstorms Likely | 0 to 3 mph SW | 71% |
| Saturday | 63°F | Patchy Fog | 1 to 5 mph E | 71% |
| Saturday Night | 53°F | Showers And Thunderstorms Likely | 5 mph E | 74% |
| Sunday | 56°F | Showers And Thunderstorms | 5 mph E | 99% |
| Sunday Night | 51°F | Showers And Thunderstorms | 1 to 5 mph E | 96% |
| Monday | 58°F | Rain Showers Likely | 1 to 5 mph E | 64% |
| Monday Night | 51°F | Chance Rain Showers then Mostly Cloudy | 5 mph SE | 33% |
| Tuesday | 68°F | Mostly Sunny | 5 to 9 mph S | 14% |
| Tuesday Night | 56°F | Chance Rain Showers then Partly Cloudy | 3 to 7 mph S | 28% |
| Wednesday | 74°F | Mostly Sunny then Chance Showers And Thunderstorms | 6 mph S | 29% |
| Wednesday Night | 56°F | Slight Chance Showers And Thunderstorms then Mostly Clear | 5 mph SW | 21% |
| Thursday | 75°F | Mostly Sunny | 2 to 6 mph NE | 8% |
| Thursday Night | 56°F | Partly Cloudy | 5 mph S | 8% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Keystone, SD
Last spring frost
May 15
First fall frost
Oct 1
Growing season
138 days
Hardiness zone
5a
Explore more for Keystone, SD: full frost dates · planting calendar · South Dakota frost dates
Climate data from the nearest NOAA station, Mt Rushmore Nmem, Sd (1.6 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.