Method

What each layer is

2 m air tiles

~100 m tiles of 2 m air temperature for the hour you pick. Mean, max, and share of tiles above a threshold come from this snapshot.

Hours vs streak

Exceedance is total hours above the threshold. Persistence is the longest consecutive run. Both are duration layers on the same grid — not a new heatmap recipe. Pick From = To for one day, or a window up to 7 days. The duration API is one day or a range-of-days product — not a custom 3-day exceedance. Air tiles, shade, and comfort still use From + Hour.

Unrelieved-heat ratio

Unrelieved-heat ratio is a HeatCast index: mean longest consecutive streak ÷ mean total hours above threshold, clipped to 0–1. Near 1 means those hours arrived as one unbroken run (no below-threshold recovery window in the scored period). It is not a NIOSH work/rest table or WBGT limit. NIOSH states that continuous work in the heat is not advisable and rest breaks let the body cool; OSHA’s proposed high-heat trigger would require a 15-minute paid rest at least every two hours. Formula: unrelieved_heat_ratio = min(1, max(0, mean_streak_hours / mean_hours_above)). NIOSH Heat Stress: Work/Rest Schedules (2017-127) · OSHA proposed heat standard.

Range ΔT

When From ≠ To, Score fetches a second 2 m air snapshot at To + the same Hour and subtracts From. Positive tiles got hotter. ΔT edges is a crude |∇ΔT| on the 100 m grid — park-vs-parking-lot boundaries, noisy, not a heat flux. Play only previews Hour; it does not recompute ΔT.

CDC SVI

Census tracts from CDC/ATSDR Social Vulnerability Index 2022, drawn as an SVG overlay and joined to tiles in the box.

OSM indoor pins

OpenStreetMap libraries, community centres, social facilities, and town halls in the box. Sports centres can appear on the map but are not walk destinations.

OSRM walk

Walking geometry from the hotspot to the nearest indoor OSM site. A thin access check — not a citywide cool-route optimizer.

SunCalc shade

OSM building footprints plus sun altitude/azimuth for the chosen hour. Approximate umbra length, not measured shade or tree canopies.

Literature canopy

A slider that estimates a small air-temperature change from added canopy (about 0.015 °C per 1%, capped). Pins you plant are visual. Neither is a new satellite or heatmap run.

Tools workspace

A separate /tools hub — not scorecard tabs. Site hours is an Open-Meteo hourly table (air / apparent / humidity / cooling-demand proxy). Peak and compound stay heat-load and heat+RH/AQI. Shift window is the coolest daylight 4 h from Open-Meteo heat + GHI — not grid carbon. Cooling plan attributes literature ΔT (canopy + labeled roof/pavement) on Open-Meteo air, then FortyGuard mean after Score. Walk exposure routes OSM indoor space from the box center, then samples TCM after Score. District score is a 0–100 HeatCast index from mean air, exceedance, and unrelieved streak (optional SVI) — not insurance.

What it is not

• An official cooling-center network or scraped city list.
• UTCI, NWS HeatRisk, or a comfort index treated as the score.
• A new heatmap generated from trees or land-surface temperature cooling.
• An animated ΔT movie. Range ΔT is two TCM snapshots at the scored Hour (To − From); Play does not recompute it.
• Coverage outside the United States.
• Grid carbon intensity, gCO2/kWh, insurance scores, or invented CO2 / methane.