Steffan Reservoir Weather Forecast
- 72
- 94
Rain Showers Likely
- 71
- 89
Chance Thunderstorms
- 74
- 92
Rain Showers Likely
- 63
- 88
Slight Chance Rain Showers
- 62
- 83
Partly Sunny
- 65
- 85
Partly Sunny
Today 5 Sep Knox
Mostly cloudy with Showers likely with a slight chance of Thunderstorms in the Morning, then mostly sunny with a slight chance of Showers in the afternoon. Humid with Highs in the mid 90s. East Winds 5 to 10 Mph, becoming southeast 10 to 15 Mph in the afternoon. Chance of rain 70 percent. Heat index Values up to 102 in the afternoon.
Tonight 5 Sep Knox
Mostly cloudy. A chance of Showers with a slight chance of Thunderstorms after midnight. Humid with Lows in the lower 70s. Southeast Winds 5 to 10 Mph. Chance of rain 50 percent.
Steffan Reservoir Temperature Statistics
September Temperature
Yankton, Chan Gurney Municipal Airport (11.2 miles)
Lowest 2 September, 2026
66.9 °FAverage September
77.6 °FHighest 2 September, 2026
91.9 °F
Climate (2021–2026)
Yankton, Chan Gurney Municipal Airport (11.2 miles)
Average Low 2021–2026
39.3 °FAverage 2021–2026
50.5 °FAverage High 2021–2026
61.8 °F