| 2023 Hardiness Zone: | Zone 4b: -25°F to -20°F |
| 2012 Hardiness Zone: | Zone 4a: -30°F to -25°F |
| 1990 Hardiness Zone: | Zone 3b: -35F to -30F |
| Average First Frost Date: | Sep. 21 - Sep. 30 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 51h - St. Croix Outwash Plain |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 55398 - Zimmerman, MN | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 0 | 7 | 20 | 33 | 45 | 54 | 59 | 57 | 47 | 36 | 22 | 7 | 32 |
| Avg Max Temp (°F) | 21 | 28 | 40 | 57 | 70 | 78 | 82 | 80 | 71 | 58 | 39 | 25 | 54 |
| Avg Precip (In.) | .94 | .76 | 1.62 | 2.3 | 3.3 | 4.48 | 4.09 | 4.38 | 3.11 | 2.31 | 1.83 | .84 | 29.96 |