Merrill, Oregon has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from -0.3 °C (low) to 16.2 °C (high). Annual precipitation averages 296.9 Millimeters. Merrill is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.9 °C | 5.2 °C | 37.08 mm |
| February | -4.7 °C | 7.6 °C | 26.42 mm |
| March | -3.1 °C | 10.7 °C | 30.48 mm |
| April | -1.6 °C | 13.9 °C | 25.4 mm |
| May | 2.2 °C | 19.1 °C | 36.58 mm |
| June | 4.9 °C | 23.6 °C | 17.53 mm |
| July | 7.9 °C | 29.1 °C | 6.86 mm |
| August | 6.7 °C | 28.6 °C | 6.86 mm |
| September | 2.8 °C | 25 °C | 10.41 mm |
| October | -1.4 °C | 17.8 °C | 20.57 mm |
| November | -4.2 °C | 9.5 °C | 33.53 mm |
| December | -6.6 °C | 4.5 °C | 45.21 mm |
| Annual | -0.3 °C | 16.2 °C | 296.93 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |