Dew point (Magnus) API

Computes dew point, frost point, and saturation/actual vapor pressure from temperature and relative humidity using the Magnus-Tetens approximation, plus the temperature-dew spread. Answers 'What is the dew point at 25C and 60% RH?', 'How close are we to fog?'.

Price$0.04per request

MethodPOST

Route/v1/climate/dew-point

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

dew-pointfrost-pointmagnusvapor-pressurehumidityweathercondensationpsychrometrics

API URLhttps://x402.hexl.dev/v1/climate/dew-point

Integration docs

Example request

{
  "tempC": 25,
  "relativeHumidity": 60
}

Example response

{
  "dewPointC": 16.69,
  "frostPointC": 17.79,
  "saturationVaporPressureHpa": 31.601,
  "actualVaporPressureHpa": 18.96,
  "tempDewSpreadC": 8.31,
  "relativeHumidity": 60,
  "interpretation": "Dew point 16.7°C; spread 8.3°C (smaller spread = closer to fog/condensation).",
  "formula": "Magnus-Tetens approximation, Sonntag (1990) coefficients a=17.62, b=243.12°C"
}

Input schema

{
  "type": "object",
  "required": [
    "tempC",
    "relativeHumidity"
  ],
  "properties": {
    "tempC": {
      "type": "number",
      "description": "Air temperature in Celsius",
      "examples": [
        25
      ]
    },
    "relativeHumidity": {
      "type": "number",
      "description": "Relative humidity in percent (0.01-100)",
      "examples": [
        60
      ]
    }
  }
}

Output schema

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