| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | May 1 - May 10 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 54a - Illinois/Indiana Prairies |
| Heat Zone Days: | 1 - 7 days Over 86°F |
Annual Climate Data for ZIP Code 46410 - Merrillville, IN | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 14 | 19 | 28 | 38 | 48 | 58 | 63 | 62 | 54 | 42 | 32 | 21 | 40 |
| Avg Max Temp (°F) | 31 | 36 | 47 | 58 | 70 | 80 | 84 | 82 | 76 | 64 | 49 | 36 | 59 |
| Avg Precip (In.) | 1.91 | 1.58 | 2.72 | 3.62 | 3.94 | 4.43 | 3.67 | 3.76 | 3.6 | 2.98 | 3.42 | 2.58 | 38.22 |