| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F | |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°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: | Dfb - Humid Continental Mild Summer, Wet All Year | |
| Ecoregion: | 59d - Boston Basin | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 02451 - Waltham, MA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 16 | 19 | 27 | 36 | 46 | 55 | 61 | 60 | 51 | 40 | 32 | 22 | 39 |
| Avg Max Temp (°F) | 35 | 38 | 47 | 58 | 69 | 78 | 83 | 81 | 73 | 62 | 51 | 40 | 59 |
| Avg Precip (In.) | 4.26 | 3.43 | 4.23 | 4.09 | 3.67 | 3.6 | 3.65 | 3.64 | 3.81 | 4.16 | 4.46 | 4.12 | 47.13 |