Deep River, Ontario climate data is summarized below. Average annual temperatures range from -0.3 °C (low) to 11 °C (high). Annual precipitation averages 655 Millimeters. 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 | -16.25 °C | -6.06 °C | 0 mm |
| February | -16.35 °C | -5.04 °C | 0 mm |
| March | -9.43 °C | 1.9 °C | 19 mm |
| April | -0.85 °C | 11.11 °C | 64 mm |
| May | 5.68 °C | 19.51 °C | 71 mm |
| June | 11 °C | 24.12 °C | 79 mm |
| July | 13.42 °C | 26.41 °C | 103 mm |
| August | 12.8 °C | 25.19 °C | 98 mm |
| September | 8.08 °C | 20.43 °C | 85 mm |
| October | 3.08 °C | 12.73 °C | 93 mm |
| November | -3.06 °C | 5.35 °C | 42 mm |
| December | -11.29 °C | -3.06 °C | 1 mm |
| Annual | -0.3 °C | 11 °C | 655 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 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |