Forecast Engine — Status & Data

Weather.city runs on a self-hosted forecast stack built entirely on official U.S. government weather data. No third-party forecast API is queried when you load a page. Here is every source we use, where it comes from, and how often it refreshes — full transparency.

Live Status

NDFD FORECAST

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checking latest run

NBM CROSS-CHECK

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checking latest run

SURFACE OBS

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reporting stations

LATEST OBSERVATION

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freshness sample

Data Sources

PRIMARY FORECAST

NOAA NWS NDFD

SINGLE SOURCE

What it is: The National Digital Forecast Database — the official National Weather Service gridded forecast, produced by human forecasters at your local NWS office.
Resolution: 2.5 km CONUS grid, out to 7 days.
Elements: Temperature, apparent temperature (feels-like), dew point, humidity, sky cover, wind, 12-h precip chance, QPF, and daily highs/lows.
Why single: NDFD is our only forecast source, so the site never jitters between providers. Every temperature you see is the official NWS number.
Origin: digital.weather.gov · public domain

CONFIDENCE

NOAA NBM

CROSS-CHECK

What it is: The National Blend of Models — NOAA's statistical blend of dozens of numerical models into a single calibrated guidance suite.
How we use it: Purely as an independent second opinion. Where NDFD and NBM daily highs/lows agree, we mark HIGH confidence; where they diverge, we flag it.
Elements: Temperature and daily max/min for the agreement check.
Origin: blend.mdl.nws.noaa.gov · public domain

OBSERVATIONS

NWS AWC METARs

LIVE OBS

What it is: Real surface observations from ~2,600 U.S. ASOS/AWOS stations, via the NOAA Aviation Weather Center METAR feed.
Backup: The Iowa Environmental Mesonet backfills gaps and history.
Store: A 30-day rolling archive powers current conditions, the meteogram's observed history, and recent-climate summaries.
Origin: aviationweather.gov · IEM

HAZARDS

NWS Alerts

SILENT FEED

What it is: Active watches, warnings and advisories from the official api.weather.gov alerts service, shown on every affected point.
Refresh: Fetched live for the point you're viewing.
Origin: api.weather.gov · public domain

IMAGERY

NWS RIDGE Radar

RADAR

What it is: NEXRAD radar mosaics and single-site imagery from the NWS RIDGE service.
Origin: radar.weather.gov · public domain

RENDERING

GrADS 3.0 · self-hosted

MAPS

What it is: Bespoke weather maps rendered in-house from the NDFD grids with our own GrADS 3.0 build — no external tile or map provider.
Independence: Forecast fields are mirrored to our own store; at runtime the site talks only to api.weather.city.

Update Cadence

Data stream	Refreshes	Source
NDFD forecast	~hourly NWS pushes updates through the day; we mirror each cycle	NWS NDFD
NBM cross-check	hourly	NOAA NBM
Surface observations	every 20 min	AWC / IEM
Active alerts	live per request (≈2-min cache)	api.weather.gov
Radar imagery	~10 min	NWS RIDGE
Bespoke maps	per cycle warm-rendered each NDFD run	GrADS 3.0

How it fits together. When you open a city page, Weather.city pulls the NDFD forecast for that exact point, the nearest live surface observation, the NBM cross-check, and any active NWS alerts — all from our own api.weather.city, which serves a locally-mirrored copy of the official NOAA/NWS data. Nothing on the page depends on a commercial weather API. Temperatures are in °F; times are shown in each location's local time zone.