| 1 | -60 to -50 | Fairbanks, AK (interior) | Mid Jun | Mid Aug | Under 60 days |
| 2 | -50 to -40 | Parts of interior Alaska | Early Jun | Late Aug | 60-90 days |
| 3 | -40 to -30 | International Falls, MN; northern ND | Mid - late May | Mid Sep | About 100-120 days |
| 4 | -30 to -20 | Minneapolis, MN; Burlington, VT | Mid May | Late Sep | About 120-140 days |
| 5 | -20 to -10 | Chicago, IL; Des Moines, IA; Albany, NY | Late Apr - early May | Early - mid Oct | About 150-165 days |
| 6 | -10 to 0 | St. Louis, MO; Columbus, OH; Boston, MA | Mid - late Apr | Mid - late Oct | About 170-190 days |
| 7 | 0 to 10 | Nashville, TN; Oklahoma City, OK; Washington, DC | Early - mid Apr | Late Oct - early Nov | About 190-210 days |
| 8 | 10 to 20 | Atlanta, GA; Dallas, TX; Seattle, WA | Mid - late Mar | Mid Nov | About 230-250 days |
| 9 | 20 to 30 | Orlando, FL; Houston, TX; Sacramento, CA | Feb - early Mar | Late Nov - Dec | About 270-300 days |
| 10 | 30 to 40 | West Palm Beach, FL; Los Angeles, CA | Rare or no frost | Rare or no frost | Nearly year-round |
| 11 | 40 to 50 | Key West, FL; Honolulu, HI | No frost | No frost | Year-round |
| 12 | 50 to 60 | Parts of Hawaii; Puerto Rico | No frost | No frost | Year-round |
| 13 | 60 to 70 | Coastal Puerto Rico | No frost | No frost | Year-round |
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