{
  "address": "c19a020cbef432db83f1331da2850525",
  "category": "other",
  "question": "Using the NWS Rothfusz regression, what is the heat index at 90 degrees F and 50% relative humidity?",
  "answer": "95 degrees F",
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  "answeredBy": "method",
  "madeAt": "2026-09-30T22:39:30.722Z",
  "validUntil": null,
  "validityClass": "forever",
  "sources": [
    {
      "label": "The Heat Index Equation (Rothfusz regression)",
      "url": "https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml"
    }
  ],
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  "source": {
    "kind": "url",
    "value": "https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml",
    "retrieved_utc": "2026-09-30T19:53:00Z"
  },
  "qsha256": "e843c6bbaba678624e6dd78267770fe82005544768d74e6529cdc2291eadbb6f",
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  "cardContractVersion": "card_contract/1",
  "deck_id": "method-deck",
  "deck_title": "Method Deck",
  "method": {
    "name": "Heat index (US NWS Rothfusz regression)",
    "version": "1",
    "source_url_or_file": "methods/heat-index-us-nws.cjs",
    "sha256_of_method_file": "36bf2096c44b7334b3658c42f92b283d8020c453cc0ba92a50d04a8a4d9339b0"
  },
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  "method_deck": {
    "inputs": [
      {
        "name": "temp_f",
        "type": "number",
        "unit": "degrees F",
        "required": true,
        "description": "Air temperature.",
        "min": 80,
        "max": 110
      },
      {
        "name": "relative_humidity_percent",
        "type": "number",
        "unit": "%",
        "required": true,
        "description": "Relative humidity.",
        "min": 40,
        "max": 100
      }
    ],
    "outputs": [
      {
        "name": "heat_index_f",
        "unit": "degrees F",
        "description": "Heat index (apparent temperature)."
      }
    ],
    "steps": [
      "Rothfusz regression: HI = -42.379 + 2.04901523*T + 10.14333127*R - 0.22475541*T*R - 0.00683783*T*T - 0.05481717*R*R + 0.00122874*T*T*R + 0.00085282*T*R*R - 0.00000199*T*T*R*R, where T is temperature in F and R is relative humidity in percent.",
      "This card uses the base regression only, valid for approximately T from 80 to 110 F and R from 40 to 100 percent; NWS applies small additional adjustments outside a normal humidity band (very low or very high RH) that this card does not include.",
      "Round to the nearest whole degree."
    ],
    "constants": [],
    "examples": [
      {
        "name": "worked example",
        "inputs": {
          "temp_f": 90,
          "relative_humidity_percent": 50
        },
        "expected": {
          "answer": "95 degrees F"
        },
        "check": "By hand, summing each regression term at T=90, R=50: -42.379 + 184.4114 + 507.1666 - 1011.3993 - 55.3864 - 137.0429 + 497.6397 + 191.8845 - 40.2975 = 94.60, rounding to 95."
      },
      {
        "name": "test vector: hotter and drier",
        "inputs": {
          "temp_f": 100,
          "relative_humidity_percent": 40
        },
        "expected": {
          "answer": "109 degrees F"
        },
        "check": "By hand, summing each regression term at T=100, R=40: -42.379 + 204.9015 + 405.7333 - 899.0216 - 68.3783 - 87.7075 + 491.496 + 136.4512 - 31.84 = 109.26, rounding to 109."
      }
    ],
    "disclaimer": null,
    "deck_category": "other"
  },
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  "kind": "method",
  "provenanceClass": "own_question",
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        "source": {
          "kind": "url",
          "value": "https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml",
          "retrieved_utc": "2026-09-30T19:53:00Z"
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        "added_by": "method:Heat index (US NWS Rothfusz regression)",
        "why": "the method that computed this answer",
        "check": null,
        "status_label": "pending",
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  }
}