Oakham, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.7 °C (low) to 13.6 °C (high). Annual precipitation averages 1230.9 Millimeters. Oakham is located in USDA Plant Hardiness Zone 6a. 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 | -9.8 °C | -0.1 °C | 92.71 mm |
| February | -9.2 °C | 1.4 °C | 81.79 mm |
| March | -4.8 °C | 5.8 °C | 103.89 mm |
| April | 1.2 °C | 12.9 °C | 99.82 mm |
| May | 6.9 °C | 19.1 °C | 93.47 mm |
| June | 12.1 °C | 23.8 °C | 108.2 mm |
| July | 15.2 °C | 26.9 °C | 105.41 mm |
| August | 14.3 °C | 25.9 °C | 111.51 mm |
| September | 10.2 °C | 21.7 °C | 110.24 mm |
| October | 3.9 °C | 14.8 °C | 122.17 mm |
| November | -1.2 °C | 8.7 °C | 93.98 mm |
| December | -6.1 °C | 2.8 °C | 107.7 mm |
| Annual | 2.7 °C | 13.6 °C | 1230.89 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |