Deep River, Ontario climate data is summarized below. Average annual temperatures range from 31.5 °F (low) to 51.9 °F (high). Annual precipitation averages 25.8 Inches. Deep River is located in USDA Plant Hardiness Zone 4b. 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 | -26.8 °F | -21.1 °F | 0 in. |
| February | -26.9 °F | -20.6 °F | 0 in. |
| March | -23 °F | -16.7 °F | 482.6 in. |
| April | -18.3 °F | -11.6 °F | 1625.6 in. |
| May | -14.6 °F | -6.9 °F | 1803.4 in. |
| June | -11.7 °F | -4.4 °F | 2006.6 in. |
| July | -10.3 °F | -3.1 °F | 2616.2 in. |
| August | -10.7 °F | -3.8 °F | 2489.2 in. |
| September | -13.3 °F | -6.4 °F | 2159 in. |
| October | -16.1 °F | -10.7 °F | 2362.2 in. |
| November | -19.5 °F | -14.8 °F | 1066.8 in. |
| December | -24.1 °F | -19.5 °F | 25.4 in. |
| Annual | 31.5 °F | 51.9 °F | 25.8 in. |
| 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 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |