Thompson, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.8 °C (low) to 15.1 °C (high). Annual precipitation averages 1280.2 Millimeters. Thompson is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | 1.8 °C | 100.58 mm |
| February | -7.7 °C | 3.2 °C | 87.12 mm |
| March | -3.6 °C | 7.4 °C | 114.55 mm |
| April | 2 °C | 14.4 °C | 114.3 mm |
| May | 7.7 °C | 20.3 °C | 89.41 mm |
| June | 12.8 °C | 24.8 °C | 111 mm |
| July | 16.2 °C | 27.7 °C | 100.33 mm |
| August | 15.2 °C | 26.7 °C | 109.47 mm |
| September | 11.2 °C | 22.9 °C | 106.68 mm |
| October | 4.9 °C | 16.4 °C | 124.46 mm |
| November | -0.3 °C | 10.4 °C | 102.11 mm |
| December | -4.9 °C | 4.7 °C | 120.14 mm |
| Annual | 3.8 °C | 15.1 °C | 1280.15 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |