Mattawa, Ontario climate data is summarized below. Average annual temperatures range from 31.8 °F (low) to 51 °F (high). Annual precipitation averages 25.7 Inches. Mattawa 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 | -21.2 °F | 0 in. |
| February | -27 °F | -20.8 °F | 0 in. |
| March | -23.1 °F | -17 °F | 406.4 in. |
| April | -18.6 °F | -12.3 °F | 1524 in. |
| May | -14.4 °F | -7.2 °F | 1803.4 in. |
| June | -11.4 °F | -4.7 °F | 2082.8 in. |
| July | -10.1 °F | -3.5 °F | 2514.6 in. |
| August | -10.3 °F | -4 °F | 2540 in. |
| September | -13 °F | -6.6 °F | 2286 in. |
| October | -15.9 °F | -10.8 °F | 2387.6 in. |
| November | -19.4 °F | -15 °F | 1016 in. |
| December | -24.3 °F | -19.6 °F | 0 in. |
| Annual | 31.8 °F | 51 °F | 25.67 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 |