Romulus, Michigan has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 15.3 °C (high). Annual precipitation averages 880.9 Millimeters. Romulus is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.8 °C | 0.2 °C | 60.71 mm |
| February | -7.3 °C | 1.8 °C | 52.32 mm |
| March | -2.8 °C | 7.6 °C | 62.48 mm |
| April | 3.1 °C | 14.8 °C | 80.01 mm |
| May | 9.3 °C | 21.5 °C | 93.47 mm |
| June | 14.7 °C | 26.7 °C | 85.85 mm |
| July | 16.9 °C | 28.9 °C | 82.8 mm |
| August | 16.1 °C | 27.8 °C | 84.58 mm |
| September | 11.9 °C | 24.2 °C | 79.76 mm |
| October | 5.7 °C | 17.1 °C | 72.64 mm |
| November | 0.2 °C | 9.5 °C | 66.8 mm |
| December | -4.3 °C | 3.1 °C | 59.44 mm |
| Annual | 4.6 °C | 15.3 °C | 880.86 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |