Every number on the map traces to a named source, and different parts of the page can come from different sources — deliberately. This page explains exactly how each one is built, including the tradeoffs.
Forecasts come from the Canadian GEMmodel family (up to 2.5 km resolution over Calgary), fetched through Open-Meteo. This is the same model behind Environment Canada's own forecasts. We query 21 separate points — 9 Calgary districts and 12 surrounding towns and mountain locations — so each area gets its own reading rather than one city-wide average. Data refreshes every 10 minutes on our side; the model itself is rerun by ECCC every 6–12 hours.
A forecast model can disagree with reality at a specific spot and moment. For zones within 25 km of Calgary International (CYYC) or Springbank (CYBW) airports, current temperature, wind and sky condition are corrected with the live airport observation (METAR), when it is under 90 minutes old. The blend is honest in both directions: real rain the model missed is shown, and model rain the station and radar disprove is removed. Cloud reports are height-aware — high cirrus at 20,000 ft is not painted as an overcast day. Every blended reading says so in the popup ("observed at CYYC · 9 km away"), and zones with no station nearby stay pure model rather than borrowing a reading that doesn't represent them.
Rain showers are patchy: the airport can report a shower while your street is dry. When precipitation is in play, we check Environment Canada's 1 km rain radar at the exact zone coordinates and suppress precipitation the radar cannot see there.
The map shows official Environment Canada warnings and watches, polled every 2 minutes from ECCC's public alert API with exact polygon matching per zone — always labelled as Environment Canada's. Our own 30-minute hail/storm forecastcomes from the model's short-range signal and is labelled as a forecast. Precedence is fixed: an official warning outranks everything; a regional watch never masks a sharper local signal. Always follow official alerts for safety decisions.
The graded None→Severe scale scores each of the next 12 hours on the model's convective energy (CAPE), storm codes and precipitation probability, and takes the worst hour. During an official warning or watch that names hail, the gauge is floored to match — and the caption then says the number came from Environment Canada, not the model.
Air quality is the Canadian Air Quality Health Index, computed with Environment Canada's published formula from ozone, nitrogen dioxide and PM2.5 together — not a PM2.5-only index, which can read "good" on a high-ozone day. We use the current hour where ECCC's official number uses a 3-hour average, so ours can differ from the posted value by about a point.
When another forecast model (ICON or MET Norway) expects thunderstorms on a day our model doesn't, the 7-day strip shows a small attributed marker rather than silently changing the forecast. One model's opinion never overwrites another's numbers.
Weather rows refresh every 10 minutes and the page polls every 5; official alerts are checked every 2 minutes; radar frames update every ~6 minutes. Airport observations are hourly by nature, so a "current" sky reading can be up to about an hour behind the sky itself — that limit belongs to how METARs work, not to this site.
Questions or corrections? See the FAQ or contact us. Calgary Weather Map is independent and not affiliated with Environment Canada, the City of Calgary, or Open-Meteo.