NWS heat index API

Computes the National Weather Service 'feels-like' heat index using the full Rothfusz regression with low/high-humidity adjustments and a Steadman fallback, returning a risk category. Answers 'What is the heat index at 35C and 60% humidity?', 'Is this heat dangerous?'.

Price$0.04per request

MethodPOST

Route/v1/climate/heat-index

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

heat-indexfeels-likerothfusznwshumidityweatherthermal-comfortheat-stress

API URLhttps://x402.hexl.dev/v1/climate/heat-index

Integration docs

Example request

{
  "tempC": 35,
  "relativeHumidity": 60
}

Example response

{
  "heatIndexC": 45.05,
  "heatIndexF": 113.09,
  "tempC": 35,
  "relativeHumidity": 60,
  "method": "rothfusz",
  "riskCategory": "danger",
  "interpretation": "It feels like 45.1°C (113.1°F); risk: danger.",
  "formula": "NWS Rothfusz heat-index regression (1990) with low/high-RH adjustments"
}

Input schema

{
  "type": "object",
  "required": [
    "tempC",
    "relativeHumidity"
  ],
  "properties": {
    "tempC": {
      "type": "number",
      "description": "Air temperature in Celsius",
      "examples": [
        35
      ]
    },
    "relativeHumidity": {
      "type": "number",
      "description": "Relative humidity in percent (0-100)",
      "examples": [
        60
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}