Source: NOAA/NWS National Digital Forecast Database and the National Blend of Models, via the Forecast Network point API. Values are nearest-grid-cell — no interpolation — on a 2.5 km grid, so the answering cell can sit up to about 1.8 km from the point you asked for; the header says exactly how far. Nights are computed for the exact point. Alerts come live from the NWS public alert feed. This is not an official source — for warnings and official forecasts go to weather.gov.