Real-Time Wet Bulb Globe Temperature (WBGT)

Real-time Wet Bulb Globe Temperature (WBGT) at a geographic point using high-resolution gridded weather analysis data.

Returns WBGT for four standard surface types. Registered locations also include a site-calibrated composite value. Calculated per ISO 7243:2017 using peer-reviewed natural wet bulb and globe temperature methods.

Surfaces: grass, turf, concrete, asphalt

Risk levels (grass surface): low < 28°C | moderate 28–32°C | high 32–35°C | very_high ≥ 35°C

Response time:

• Registered locations: < 3 ms (pre-computed)
• Other locations: ~250 ms (real-time calculation)

Coverage: worldwide north of the equator. location.region names the area: CONUS, Alaska, Hawaii, Puerto Rico, Guam or Global.

source.conditions: analysis when temperature, humidity and wind come from a surface analysis that assimilates observations (the US and its territories), model when they come from a global forecast model. Model values are coarser, typically within about 2°F of an analysis value and further off in mountains and along coasts.

source.solar: model when solar radiation comes from a high-resolution forecast, cloud_cover when it is estimated from forecast cloud cover (outside the contiguous US, or when the forecast is missing), night with the sun down.

data_age_seconds: how long ago the underlying weather analysis was valid, not request latency or how recently it was computed. It is typically tens of minutes, even for a fresh response. For source.conditions model it counts from the model step at or before now (up to about 3 hours), and run names the model run.

nowcast_adjustment: a small upward correction (at most about 1°F) to the temperature input when the short-range forecast shows conditions warming, to offset the analysis age. Always 0 when the trend is flat or cooling, or when the trend data isn't available.

heat_policy (optional, e.g. heat_policy=kshsaa): adds a heat_policy object that maps each WBGT value to a published activity-modification policy's zones. It holds the policy zones (key, name, color, °F bounds and guidance text, lowest first), a zone key per surface under surfaces, and under site for registered locations. Zone thresholds are °F whatever units is. Without the parameter the response is unchanged.

"heat_policy": {
  "policy": "kshsaa",
  "name": "KSHSAA Heat Policy",
  "source": "Updated KSHSAA SMAC, April 2026",
  "zones": [
    {"key": "green", "name": "Green", "color": "#2E9E44", "min_wbgt_f": null, "max_wbgt_f": 79.9,
     "guidance": "Normal activity. Minimum 3 rest breaks/hour, 3 min each."},
    ...
  ],
  "surfaces": {"grass": "yellow", "turf": "orange", "concrete": "orange", "asphalt": "red"},
  "site": "orange"
}

curl -X GET "https://example.com/observations/wbgt/?heat_policy=kshsaa&lat=0.1&lon=0.1"