Which State Is Hottest in December
December is winter across most of the United States, so the hottest state in December is usually determined by far southern latitudes and coastal moderation. In the Lower 48, Florida is commonly the warmest state in December, with South Texas and southern Arizona also recording relatively high averages. Hawaii remains comfortably warm year round and often records the highest statewide average temperatures during December. This breakdown explains how to interpret maps of December normals, why coastal and subtropical locations stay mild, and how local December days can still vary from long-term averages.
How December Averages Are Determined
Meteorologists and climatologists define a location’s December temperature using long-term normals, typically a 30-year period such as 1991–2020. These normals smooth day-to-day variability and are updated every decade to reflect slow shifts in climate. Averages are reported as daily mean, daily high, and daily low values, usually in degrees Fahrenheit or Celsius. For December, the warmest normals in the contiguous U.S. occur over southern Florida and the southern coasts, while inland and northern areas are substantially cooler. Reliable sources include the National Centers for Environmental Information (NCEI) and the National Weather Service, which publish these normals at state, city, and gridded resolution.
Why Some States Stay Warmer in December
- Latitude: Places closer to the equator receive more direct sunlight in December, limiting the seasonal temperature drop.
- Coastal moderation: Proximity to large bodies of water stabilizes temperatures, keeping coastal areas warmer than nearby inland spots during winter nights.
- Ocean currents and regional wind patterns: For example, the Gulf Stream warms the Southeast Atlantic coast, while prevailing westerlies keep interior locations colder.
Typical Warmest States in December
Among the 48 contiguous states, Florida generally reports the highest average temperatures in December, especially in the southern half of the peninsula. South Texas, especially the coastal and lower Valley areas, and southern and coastal Arizona also rank among the warmest. In Hawaii, most sites remain in the comfortable 70s to low 80s Fahrenheit (low 20s Celsius) during December, often producing the highest statewide averages. The rankings below are illustrative based on long-term normals and can shift slightly depending on the specific 30-year period used.
| State or Region | December Average High (°F) | December Average Low (°F) | Mean Temperature (°F) | Source Type |
|---|---|---|---|---|
| Hawaii (statewide avg) | 78–83 | 64–69 | 71–76 | NOAA 1991–2020 normals |
| Florida (south peninsula) | 75–80 | 58–65 | 67–72 | NOAA 1991–2020 normals |
| South Texas (lower Valley) | 70–78 | 50–58 | 63–68 | NOAA 1991–2020 normals |
| Arizona (southern coastal) | 68–75 | 45–55 | 58–65 | NOAA 1991–2020 normals |
| California (Southern California coast) | 65–70 | 48–55 | 56–62 | NOAA 19沿海地区数据 |
Regional Variations Within States
Even within a typically warm state, December temperatures can vary widely. Inland Florida, for example, is noticeably cooler than the coasts and is prone to occasional cold snaps. South Texas is warm along the Gulf coast but cooler just a few dozen miles inland. Mountain areas of Arizona remain chilly in December despite lower desert valleys being relatively mild. Therefore, when asking about the hottest state in December, it is important to specify whether you mean the statewide average, the warmest city or region, or the location most likely to experience mild winter days. Maps of December normals at city scale show coastal bands of warmth and colder interior pockets, illustrating this internal variation.
How to Interpret Local Forecasts in December
When you see a December forecast for a specific city or state, distinguish between typical conditions and any short-term pattern. A warm front can raise temperatures for several days, while cold-air outbreaks can push readings well below normal. Check daily highs and lows, not just the day’s condition, and compare them to the 30-year normals for that location. For travel planning, focusing on average ranges helps set realistic expectations for clothing and activities. Use reliable sources such as the National Weather Service and local climate offices to understand whether a particular December day represents typical weather or an anomaly.
Practical Tips for Warmth Planning in December
If your goal is to find the warmest possible December destination in the U.S., prioritize southern Florida, the Gulf Coast of Texas, and southern Arizona, while recognizing that Hawaii often offers the mildest island setting. For outdoor activities, aim for midday when temperatures peak, and remember that evenings and shaded areas can still be cool. Pack layers even in warm locations, because humidity, wind, and rain can affect perceived comfort. Review historical normals for the specific city you plan to visit rather than relying on a broad state label, since microclimates and elevation can shift conditions significantly within short distances.
Key Takeaways
- December is winter almost everywhere in the United States, but subtropical and coastal regions remain relatively mild.
- Statewide averages show Hawaii and southern Florida as the hottest states in December, with South Texas and southern Arizona also warm.
- Local conditions vary by coast, elevation, and short-term weather patterns; always compare forecasts to long-term normals.
- Use 30-year climate normals from authoritative sources to understand typical December temperatures rather than single-day extremes.