The official National Weather Service forecast for Monmouth — 44.8484°N, 123.234°W, population 20,912, 11.7 miles from I-5. Forecasts here are written by NWS PQR, this county’s forecast office.
| Polk County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 47 | 49 | 53 | 59 | 66 | 72 | 81 | 81 | 75 | 63 | 52 | 46 | 62 |
| Avg low °F | 35 | 35 | 36 | 39 | 44 | 48 | 53 | 53 | 49 | 43 | 38 | 34 | 42 |
| Precip in | 10.7 | 7.7 | 7.9 | 5.1 | 3.0 | 1.7 | 0.3 | 0.5 | 2.1 | 5.6 | 10.3 | 12.6 | 67.5 |
1996–2025 normals for Polk County — the climate division Monmouth sits in. All-time county record high 106.1°F (2021-06-28); record low 2.1°F (1972-12-09). Source: NOAA / National Weather Service.