Bath, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.1 °C (low) to 12.7 °C (high). Annual precipitation averages 992.1 Millimeters. Bath is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.1 °C | -2.6 °C | 58.42 mm |
| February | -13.8 °C | -0.7 °C | 52.32 mm |
| March | -8.2 °C | 4.4 °C | 59.94 mm |
| April | -1.3 °C | 11.9 °C | 75.95 mm |
| May | 5.3 °C | 19.4 °C | 90.93 mm |
| June | 10.4 °C | 23.9 °C | 101.35 mm |
| July | 13.3 °C | 26.7 °C | 105.16 mm |
| August | 12.2 °C | 25.8 °C | 100.33 mm |
| September | 8.1 °C | 21.7 °C | 91.19 mm |
| October | 1.9 °C | 14.1 °C | 106.68 mm |
| November | -3.3 °C | 7 °C | 71.63 mm |
| December | -9.4 °C | 0.6 °C | 78.23 mm |
| Annual | 0.1 °C | 12.7 °C | 992.13 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |