The official National Weather Service forecast for Sisseton — 45.6647°N, 97.0498°W, 3 miles from I-29.
| Roberts County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 21 | 25 | 38 | 54 | 68 | 78 | 83 | 80 | 73 | 57 | 41 | 26 | 54 |
| Avg low °F | 3 | 6 | 19 | 32 | 44 | 56 | 60 | 58 | 49 | 36 | 23 | 10 | 33 |
| Precip in | 0.6 | 0.7 | 1.1 | 2.3 | 3.1 | 3.6 | 3.4 | 3.0 | 2.5 | 2.5 | 0.9 | 0.9 | 24.6 |
1996–2025 normals for Roberts County — the climate division Sisseton sits in. All-time county record high 103.3°F (1976-08-19); record low -37.6°F (1994-02-09). Source: NOAA / National Weather Service.