Exeter, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.9 °C (low) to 17.6 °C (high). Annual precipitation averages 1019 Millimeters. Exeter is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.5 °C | 2 °C | 55.63 mm |
| February | -5.6 °C | 4.9 °C | 49.53 mm |
| March | -0.5 °C | 11.2 °C | 70.61 mm |
| April | 5.3 °C | 18.3 °C | 102.87 mm |
| May | 11.6 °C | 23.7 °C | 121.16 mm |
| June | 16.8 °C | 28.6 °C | 127.25 mm |
| July | 18.8 °C | 30.4 °C | 101.85 mm |
| August | 17.4 °C | 29.8 °C | 90.93 mm |
| September | 12.8 °C | 26.6 °C | 85.6 mm |
| October | 6.3 °C | 19.7 °C | 78.23 mm |
| November | 0.4 °C | 11.6 °C | 75.44 mm |
| December | -4.5 °C | 4.8 °C | 59.94 mm |
| Annual | 5.9 °C | 17.6 °C | 1019.04 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |