Warmest Place in the Continental US in January: Key West, Florida

Key West, Florida is consistently the warmest location in the contiguous United States during January.

January Climate (Normals 1991–2020)

• Average High: 75°F (24°C)
• Average Low: 65°F (18°C)
• Mean: 70°F (21°C)
• Water Temp: ~72°F (22°C) — moderates air temps.

Why Key West?

• Southernmost point: 24.55° N — only US city below 25° N.
• Maritime tropical: Surrounded by warm Florida Current/Gulf Stream.
• No cold-air drainage: Flat, no interior continental influence.

Runners-Up

• Miami/Fort Lauderdale: Avg ~68°F (20°C) — slightly cooler nights.
• Naples, Marco Island: Similar but occasionally cooler.
• Yuma, AZ / Phoenix: Warm days (70°F) but cold nights (40s°F) — large diurnal range.
• Brownsville, TX: ~65°F mean — but occasional freezes.

Non-Contiguous

Honolulu (78°F mean), San Juan, PR (77°F), Guam, USVI — warmer, but not "continental US."