Climate almanac
Monmouth
Illinois, United States · 40.91°, -90.65°
What is the climate like in Monmouth?
The best time to visit Monmouth is typically May – September, with trip comfort peaking in September (7.3/10). Monmouth is warmest in July, when daily highs average 86°F (30°C), and coolest in January, when lows fall to about 20°F (-7°C). The wettest month is typically May and the driest is November; the year sees roughly 39 in (996 mm) of precipitation.
- Best time to visitMay – September — comfort peaks in September (7.3/10)
- Warmest monthJuly — average high 86°F (30°C)
- Coolest monthJanuary — average low 20°F (-7°C)
- Wettest monthMay (4.9 in (124 mm))
- Driest monthNovember (2.0 in (50 mm))
- Annual precipitation39 in (996 mm)
- Based on2016-2025 daily ERA5 reanalysis data (10-year normals)
- Records fromMonmouth, 4 km away (1893-2026)