St. Louis Heat Index Today
Updated planning preview · 10:00 PM forecast from WeatherAPI
Heat index
64°F
Low
Routine outdoor plans are generally reasonable.
Temperature
64°F
Humidity
42%
Estimated WBGT
12.7°C
UV index
0.0
Best outdoor window
8:00 AM–12:00 PM
Lowest combined heat and UV load in the available hourly preview.
Hourly heat risk
WBGT values are labeled as modeled estimates until a provider supplies measured readings.
| Time | Temperature | Heat index | Estimated WBGT | UV | Risk |
|---|---|---|---|---|---|
| 8 AM | 59°F | 59°F | 13.0°C | 0.2 | Low |
| 10 AM | 67°F | 67°F | 15.9°C | 2.0 | Low |
| 12 PM | 74°F | 75°F | 18.0°C | 4.6 | Low |
| 2 PM | 79°F | 77°F | 19.2°C | 4.6 | Low |
| 4 PM | 81°F | 78°F | 19.5°C | 2.0 | Low |
| 6 PM | 77°F | 75°F | 18.5°C | 0.2 | Low |
| 9 AM | 69°F | 69°F | 16.9°C | 0.7 | Low |
| 11 AM | 78°F | 78°F | 20.4°C | 3.3 | Low |
Today's outlook
In St. Louis, the highest modeled heat burden in this preview occurs around 11:00 AM. The recommended window is selected from the lowest combined risk score, temperature, and UV—not from generic city copy.
Three-day forecast
Monday
Heat index up to 76°F
78°F / 55°F
LowTuesday
Heat index up to 78°F
81°F / 57°F
LowWednesday
Heat index up to 86°F
89°F / 62°F
ModerateToday in St. Louis
What changes across the day
Based on the available hourly WeatherAPI forecast
Peak heat index
78°F at 4:00 PM
The preview low is 59°F around 8:00 AM.
Feels-like difference
Matches air temp
Current humidity is 42%, one input that changes evaporative cooling.
Peak UV
4.6 at 12:00 PM
UV and heat are separate hazards; the lowest-heat hour may still need sun protection.
Tomorrow's direction
2°F hotter tomorrow
Today's forecast range is 55°F–78°F.
Where these numbers come from
WeatherAPI supplies the forecast. HeatGuard calculates heat-index risk and models WBGT from forecast temperature, humidity and a daytime solar allowance. Modeled WBGT is not an on-site globe-thermometer reading.
Local planning context
Planning for heat in St. Louis, MO
St. Louis heat risk can change quickly with humidity, cloud cover and the timing of a weather system. Use the hourly values rather than a single daily high, and reassess when the activity lasts into a warmer part of the day.
Forecasts describe outdoor conditions, not an individual's medical risk. Workload, duration, shade, clothing, acclimatization and health can change the appropriate decision.
Nearby forecasts
Keep planning
Track St. Louis in HeatGuard
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