Prospect, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 3 °C (low) to 17.7 °C (high). Annual precipitation averages 1067.8 Millimeters. Prospect is located in USDA Plant Hardiness Zone 8a. 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 | -1.7 °C | 7.9 °C | 161.04 mm |
| February | -1.4 °C | 10.2 °C | 99.06 mm |
| March | -0.2 °C | 12.5 °C | 118.11 mm |
| April | 1.4 °C | 14.7 °C | 100.58 mm |
| May | 4.5 °C | 19.7 °C | 67.31 mm |
| June | 6.9 °C | 23.7 °C | 37.85 mm |
| July | 9.9 °C | 29.8 °C | 15.75 mm |
| August | 9.3 °C | 29.9 °C | 15.24 mm |
| September | 6.3 °C | 26.6 °C | 25.91 mm |
| October | 2.7 °C | 18.9 °C | 75.95 mm |
| November | 0.2 °C | 11 °C | 156.97 mm |
| December | -1.8 °C | 7.2 °C | 194.06 mm |
| Annual | 3 °C | 17.7 °C | 1067.83 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |