Declo, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 1.6 °C (low) to 16.3 °C (high). Annual precipitation averages 267.5 Millimeters. Declo is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.2 °C | 2.4 °C | 29.72 mm |
| February | -5.4 °C | 5.3 °C | 18.03 mm |
| March | -2.2 °C | 11.1 °C | 25.4 mm |
| April | 0.4 °C | 15.1 °C | 27.69 mm |
| May | 4.8 °C | 20.3 °C | 37.59 mm |
| June | 8.5 °C | 25.4 °C | 19.81 mm |
| July | 12.1 °C | 31.2 °C | 6.6 mm |
| August | 11 °C | 30.7 °C | 11.43 mm |
| September | 6.4 °C | 25.1 °C | 16 mm |
| October | 1.2 °C | 17.3 °C | 21.84 mm |
| November | -3.7 °C | 8.9 °C | 22.1 mm |
| December | -7.1 °C | 2.7 °C | 31.24 mm |
| Annual | 1.6 °C | 16.3 °C | 267.45 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |