Foster, Rhode Island has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.1 °C (low) to 14.6 °C (high). Annual precipitation averages 1344.9 Millimeters. Foster 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 | -7.4 °C | 1.7 °C | 109.22 mm |
| February | -7.1 °C | 3 °C | 92.96 mm |
| March | -3.2 °C | 7.1 °C | 128.27 mm |
| April | 2.2 °C | 14.1 °C | 119.89 mm |
| May | 7.7 °C | 20 °C | 93.98 mm |
| June | 12.9 °C | 24 °C | 112.52 mm |
| July | 16.1 °C | 27.1 °C | 95.5 mm |
| August | 15.3 °C | 25.9 °C | 113.79 mm |
| September | 11.4 °C | 22.1 °C | 108.2 mm |
| October | 5.5 °C | 15.8 °C | 130.3 mm |
| November | 0.2 °C | 10 °C | 110.74 mm |
| December | -4.3 °C | 4.4 °C | 129.54 mm |
| Annual | 4.1 °C | 14.6 °C | 1344.91 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 |