Heat Index Climatological Exceedance Counter
Count exposure above caller heat-index threshold using explicitly domain-restricted Rothfusz base regression, not the existing Steadman apparent-temperature tool; no low-RH adjustment or heat-health/work safety certification.
Description
The heat index estimates apparent warmth from air temperature and relative humidity.
The heat index estimates apparent warmth from air temperature and relative humidity. This tool summarizes exposure within the supported hot-weather range rather than applying the regression indiscriminately to cool or very dry conditions.1, 2
Count exposure above caller heat-index threshold using explicitly domain-restricted Rothfusz base regression, not the existing Steadman apparent-temperature tool; no low-RH adjustment or heat-health/work safety certification.
When to use Heat Index Climatological Exceedance Counter
Use this tool to count exposure above caller heat-index threshold using explicitly domain-restricted Rothfusz base regression, not the existing Steadman apparent-temperature tool; no low-RH adjustment or heat-health/work safety certification.
Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
How to use Heat Index Climatological Exceedance Counter and understand its results
- Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
- Enter observedTemperaturesC, relativeHumidityFractions, representedHours, callerHeatIndexThresholdC using the field table and calculation rules, then run the tool.
- Read rothfuszHeatIndicesC, hoursAboveCallerThreshold, exposureFractionAboveCallerThreshold. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| observedTemperaturesC | Observed temperatures c | list of number | Required |
| relativeHumidityFractions | Relative humidity fractions | list of number | Required |
| representedHours | Represented hours | list of number | Required |
| callerHeatIndexThresholdC | Caller heat index threshold c | number | Required |
Enter aligned temperatures in °C, relative-humidity fractions from zero to one and positive represented hours, plus a finite heat-index threshold in °C. Each temperature must convert to 80–120 °F and each humidity to 40–100 percent. The tool evaluates the base nine-term Rothfusz polynomial in °F and percent humidity, converts each result to °C, and sums hours strictly above the threshold. It returns those hours and their fraction of total exposure.
Paired lists must be nonempty and have equal lengths.
HI_C = (RothfuszPolynomial(T_F, 100 RH) − 32) × 5/9; exceedance fraction = hours with HI_C > threshold / total hours Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| rothfuszHeatIndicesC | Rothfusz heat indices c | list of number |
| hoursAboveCallerThreshold | Hours above caller threshold | number |
| exposureFractionAboveCallerThreshold | Exposure fraction above caller threshold | number |
{
"input": {
"observedTemperaturesC": [
30,
30
],
"relativeHumidityFractions": [
0.7,
0.7
],
"representedHours": [
1,
3
],
"callerHeatIndexThresholdC": 35
},
"output": {
"rothfuszHeatIndicesC": [
35.03801755555546,
35.03801755555546
],
"hoursAboveCallerThreshold": 4,
"exposureFractionAboveCallerThreshold": 1
}
}Limitations and assumptions
This implementation uses the base polynomial without the additional humidity adjustments in the full NWS procedure. Observations outside its specified domain are input errors rather than excluded records. The index assumes a reference exposure environment and does not determine individual heat risk or workplace limits.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Humidex Monthly Statistics: Summarize measured vapor-pressure/temperature humidex across actual represented monthly exposure; no RH/dewpoint saturation reconstruction or health recommendation. For a complementary task, use Wind Chill Climatological Monthly Mean: Summarize caller observed month exposure using existing wind-chill equation only where T≤10 C and wind≥4.8 km/h; invalid observations are excluded with coverage, not computed from monthly mean weather or certified cold safety.
Further background: Heat index and the Rothfusz regression.
References
-
Heat index and the Rothfusz regression — National Weather Service
Similar or alternative tools
- Humidex Monthly Statistics
Summarize measured vapor-pressure/temperature humidex across actual represented monthly exposure; no RH/dewpoint saturation reconstruction or health recommendation.
- Wind Chill Climatological Monthly Mean
Summarize caller observed month exposure using existing wind-chill equation only where T≤10 C and wind≥4.8 km/h; invalid observations are excluded with coverage, not computed from monthly mean weather or certified cold safety.