UV Index Today in St. Louis, Missouri

Current UV
Today's Max

Hourly UV Forecast

low moderate high very high extreme

Surface Type

Reflective surfaces increase your UV exposure — snow reflects up to 90%, sand about 20%.

Safe Exposure Time

Estimated burn times based on the Fitzpatrick scale for skin color and today's maximum UV index of . Tap your skin type:

Very fair skin, always burns, never tans

Time until burn
With SPF 15*
With SPF 30*

*Assumes proper application of broad-spectrum sunscreen with reapplication every 2 hours. Estimates follow WHO guidance and satellite-derived data — see how our data works.

Sun Times

Dawn
Sunrise
Solar Noon
Sunset
Dusk
Day Length
Morning Golden Hour Ends
Evening Golden Hour

Important Safety Information

General Guidelines

These exposure times are estimates based on scientific research and should be used as general guidelines only. Individual responses to UV exposure may vary.

Affecting Factors

UV exposure is affected by: time of day, season, altitude, cloud cover, reflection from surfaces, and individual skin sensitivity.

Protection Tips

Seek shade during peak UV hours (10 AM - 4 PM), wear protective clothing, use broad-spectrum sunscreen, and monitor the UV index regularly.

Medical Advice

Consult a healthcare provider for personalized sun protection advice, especially if you have a history of skin conditions or take medications that increase sun sensitivity.

St. Louis's UV Climate

St. Louis sits on the west bank of the Mississippi River at the meeting point of humid southern air and continental midwestern weather, producing hot, sun-drenched summers with surprisingly strong UV for the Midwest. Summer gatherings in Forest Park, at the Gateway Arch grounds, and at Cardinals games put residents outdoors during peak UV hours, and the region's notorious humidity makes the sun feel oppressive well into the evening.

Average Annual UV Index

6.8

Peak UV Season

April - September

Sunny Days per Year

202

Typical UV Index by Season in St. Louis

Season Typical Midday UV Protection Needed
Summer Very High (8-9) SPF 30+, hat, sunglasses; shade from 10 AM – 4 PM
Spring & Fall Moderate to High (4-7) SPF 30+ for extended time outdoors
Winter Low (1-3) Sunscreen for long midday exposure; more on snow

UV Index in Nearby Cities

Practical Tips for Outdoor Activities

Make the most of outdoor activities while staying safe in St. Louis City County:

UV and Weather in St. Louis City County

Learn about St. Louis City 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

St. Louis has a humid continental climate with a strong subtropical influence in summer. From May through August, midday UV index values reach 8-9 on clear days — comparable to cities much farther south — while winter values drop to the low range. The transition seasons are abrupt: UV can jump from winter lows to high-range readings within a few weeks in April as the sun angle climbs quickly.

UV Index and Health Impact

Understanding UV radiation levels is crucial for protecting your health. Typical clear-day UV index values in St. Louis through the year:

  • Summer: Very High (8-9)
  • Spring/Fall: Moderate to High (4-7)
  • Winter: Low (1-3)
  • 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

Summers in St. Louis feature long stretches of hazy, hot, humid weather where thin high clouds filter the light without meaningfully reducing UV. Severe thunderstorms roll through periodically but tend to clear quickly, restoring full sun. Winters are grayer and colder, with genuine UV concern limited to snow-cover days when reflection can nearly double effective exposure for skiers and sledders.

Frequently Asked Questions About UV in St. Louis

What is the UV index in St. Louis today?

The live UV index for St. Louis, MO 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 St. Louis?

UV radiation is strongest between 10 AM and 4 PM. St. Louis's peak UV season runs April - September, when the midday index typically reaches Very High (8-9).

How high does the UV index get in St. Louis?

Summer days in St. Louis typically reach Very High (8-9). Spring and fall usually bring Moderate to High (4-7), while winter values are typically Low (1-3).

Do I need sunscreen in St. Louis during winter?

Winter UV in St. Louis is generally low; sunscreen is mainly worthwhile on sunny days with snow on the ground, when reflection significantly boosts exposure.

How sunny is St. Louis compared to other cities?

St. Louis averages about 202 sunny days per year with an average annual UV index around 6.8.