UV Index Today in Key West, Florida
Key West's UV Climate
Key West is the southernmost city in the continental United States, closer to Havana than to Miami, and it carries the continental US's most relentless UV climate. Surrounded by water on all sides, the island adds ocean reflection to an already near-tropical sun, and its vacation rhythm — snorkeling, sailing, Duval Street wandering, sunset celebrations at Mallory Square — keeps visitors outdoors from morning to dusk with no seasonal break in exposure.
Average Annual UV Index
8.8
Peak UV Season
Year-round (peak March - September)
Sunny Days per Year
259
Typical UV Index by Season in Key West
| Season | Typical Midday UV | Protection Needed |
|---|---|---|
| Summer | Extreme (10-11+) | SPF 30+, hat, sunglasses; shade from 10 AM – 4 PM |
| Spring & Fall | Very High to Extreme (8-11) | SPF 30+ for extended time outdoors |
| Winter | High (6-7) | Sunscreen for long midday exposure; more on snow |
UV Index in Nearby Cities
- UV Index in Naples, FL110 mi away
- UV Index in Miami, FL130 mi away
- UV Index in Delray Beach, FL169 mi away
- UV Index in West Palm Beach, FL184 mi away
Practical Tips for Outdoor Activities
Make the most of outdoor activities while staying safe in Monroe County:
- Check UV index and weather radar before planning outdoor activities
- Schedule outdoor activities during low UV hours
- Use appropriate sun protection based on UV levels
- Stay hydrated during outdoor activities
- Take regular breaks in shaded areas
- Monitor weather conditions for changes
- Be prepared for sudden weather changes
- Know the signs of heat-related illness
- Wear a hat and protective clothing
- Check visibility conditions before outdoor plans
- Stay alert to weather alerts and warnings
UV and Weather in Monroe County
Learn about Monroe County's unique climate patterns, UV radiation levels, and how they affect your daily life. Enter your zip code for location-specific weather radar data and UV forecasts to help you make informed decisions about outdoor activities and sun protection.
Climate and UV Patterns
Key West's tropical savanna climate produces extreme summer UV of 11+ and keeps winter midday values in the high range of 6-7 — a January reading that matches midsummer in the northern US. Being a small island, there's no inland retreat from reflective water, and boat days multiply exposure with glare from every direction. UV protection in Key West is a twelve-month requirement, not a summer habit.
UV Index and Health Impact
Understanding UV radiation levels is crucial for protecting your health. Typical clear-day UV index values in Key West through the year:
- Summer: Extreme (10-11+)
- Spring/Fall: Very High to Extreme (8-11)
- Winter: High (6-7)
- Peak UV hours: 10 AM - 4 PM
- Cloud cover can reduce UV by 20-40%, but does not eliminate it
- Clear skies bring maximum UV exposure
Local Weather Patterns
The island's weather is steadier than mainland Florida's — sea breezes moderate the heat and thunderstorms are briefer, meaning fewer cloud breaks during peak hours. The legendary water clarity that makes the reef snorkeling spectacular also lets UV penetrate several feet down, so swimmers burn while submerged. Winter cold fronts arrive diluted, usually leaving bright, breezy days where visitors underestimate a sun that still reads high at noon.
Frequently Asked Questions About UV in Key West
What is the UV index in Key West today?
The live UV index for Key West, FL is shown at the top of this page and updates throughout the day, along with today's maximum and an hourly forecast.
When is the sun strongest in Key West?
UV radiation is strongest between 10 AM and 4 PM. Key West's peak UV season runs Year-round (peak March - September), when the midday index typically reaches Extreme (10-11+).
How high does the UV index get in Key West?
Summer days in Key West typically reach Extreme (10-11+). Spring and fall usually bring Very High to Extreme (8-11), while winter values are typically High (6-7).
Do I need sunscreen in Key West during winter?
Emphatically yes. Key West's winter UV stays in the high range — stronger than a northern summer — so daily sunscreen is essential in every month.
How sunny is Key West compared to other cities?
Key West averages about 259 sunny days per year with an average annual UV index around 8.8.