Tip: Allow location in your browser settings for precise weather, or just enter temperature & humidity manually below.
Format: 9:30 or 9.5
Heat Index
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WBGT
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UV Index
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Rec. Pace
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WBGT is a stronger predictor of heat stress for outdoor exercise than Heat Index. UV is independent of temperature. Recommended pace adjusts your target for current conditions.
Heat Index (NWS, °F)
< 80°F — Caution (fatigue possible)
80–89°F — Caution
90–102°F — Extreme Caution
103–124°F — Danger
≥ 125°F — Extreme Danger
Feels-like temperature in the shade. Full sun can add up to ~15°F. Prolonged activity raises risk of cramps, exhaustion, or stroke.
WBGT (ACSM athletic guidelines, °C)
< 18°C — Low / Green Flag
18–22.9°C — Moderate / Yellow
23–27.9°C — High / Red Flag
28–32.2°C — Very High / limit intensity
≥ 32.3°C — Extreme / cancel outdoor hard efforts
Best single metric for outdoor exercise. Combines temperature, humidity, and (in true instruments) solar load & wind. Our value is an approximation from air temp + humidity only.
UV Index (WHO / EPA)
0–2 — Low
3–5 — Moderate
6–7 — High
8–10 — Very High
11+ — Extreme
Independent of heat. High UV causes sunburn and long-term skin damage even on cooler days. Use sunscreen, hat, and sunglasses at 6+.
Effort Guidance
Hydration
Notes
Estimates only • Open-Meteo + browser geolocation
WBGT uses the Australian Bureau of Meteorology approximation (temp + humidity only)
Always prioritize how you feel over any calculator