Arco, Idaho has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -2.7 °C (low) to 13.7 °C (high). Annual precipitation averages 228.4 Millimeters. Arco is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -15 °C | -1.9 °C | 21.59 mm |
| February | -12.7 °C | 0.8 °C | 19.05 mm |
| March | -6.7 °C | 6.9 °C | 18.03 mm |
| April | -2.4 °C | 13.3 °C | 23.62 mm |
| May | 2.1 °C | 18.6 °C | 31.24 mm |
| June | 5.6 °C | 24 °C | 22.61 mm |
| July | 9.2 °C | 30.2 °C | 7.37 mm |
| August | 8.2 °C | 29.4 °C | 12.19 mm |
| September | 3.6 °C | 23.6 °C | 17.53 mm |
| October | -2.1 °C | 15.3 °C | 18.29 mm |
| November | -8.3 °C | 5.9 °C | 13.46 mm |
| December | -13.7 °C | -1.3 °C | 23.37 mm |
| Annual | -2.7 °C | 13.7 °C | 228.35 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |