1. Geographic unit
The dataset covers 75 selected U.S. metros. Each city has a latitude/longitude reference point used only to locate nearby official climate stations. It does not represent every property within the metro.
2. Climate baseline
The updater targets NOAA/NCEI 1991–2020 Monthly Climate Normals. It selects a nearby station with complete temperature normals and useful precipitation coverage. The station ID, name and distance are published on each city page.
3. Snowfall is nullable
Snowfall is a separate field with three possible meanings: a measured zero, a positive normal, or unavailable. If the selected temperature station lacks adequate snowfall coverage, the updater searches nearby official stations for a usable snow series. If none is found, snowfall remains null and the city is excluded from snow rankings.
4. Recent temperature context
Recent station observations are optional. Each observed day is compared with the 1991–2020 monthly normal for that same calendar month. The displayed departure is therefore period-matched across a window that crosses month boundaries. It is still an approximation based on monthly, not daily, normals.
5. Electricity
The updater retrieves the latest available monthly residential electricity price by state from the U.S. Energy Information Administration. A city page’s rate is a statewide residential average, not the local utility tariff.
6. Climate Stress Score
100 × (0.60 × cold + 0.275 × freeze exposure + 0.125 × precipitation exposure)Cold: January normal minimum scaled from 45°F (0) to −10°F (1). Freeze exposure: months with a normal minimum below 32°F divided by seven, capped at one. Precipitation exposure: annual precipitation divided by 70 inches, capped at one.
7. Operating Cost Index
100 × clamp((rate − 10¢) ÷ 25¢, 0, 1)The dollar scenario assumes a 9 kW heater, climate-adjusted warm-up full-load-equivalent hours and 60% full-load-equivalent operation during a one-hour session.
8. Optional Planning Index
For readers who want a single composite, the Planning Index is 80% Climate Stress Score and 20% Operating Cost Index. It is not labeled as physical climate stress.
9. Update cadence
The workflow runs weekly, regenerates dependent pages and validates the output. A prior climate record is preserved if no complete nearby station can be retrieved during a run.
10. Limitations
The indexes do not model a particular enclosure, wind, solar gain, thermal bridging, heater efficiency, utility tariff, electrical service or local code. They are standardized comparisons—not guarantees, permit advice or final sizing instructions.
NOAA U.S. Climate Normals →
NCEI Access Data Service →
EIA retail electricity data →