Weather
Forecasts, Warnings & Radar
How to read a forecast, what the new coloured alerts mean, and how to use radar like a pro, all for southern Alberta.
In Simple Terms
A forecast tells you what’s likely. An alert tells you what’s dangerous. Radar shows you what’s happening right now. Use all three and you’ll rarely get caught out.
Quick habit
Check the forecast the night before, the alerts in the morning, and the radar before you head out.
Check the forecast the night before, the alerts in the morning, and the radar before you head out.
Reading a forecast
- Probability of precipitation (POP): 40% means a 4-in-10 chance that you’ll get measurable rain or snow at any given spot in the area. It does not mean it will rain 40% of the day.
- Wind and gusts: “West 40 km/h gusting to 70” matters more here than almost anything else. Gusts are what knock things over.
- Wind chill and humidex: how cold or hot it will feel on your skin. Dress for these, not the plain temperature.
- Trust it by distance: today and tomorrow are usually good. Days 3 to 5 show the trend. Days 6 and 7 are a rough guess. Watch how the forecast changes from day to day rather than locking onto one number.
Why Lethbridge is tricky
Chinooks can push the temperature up 15 to 20 degrees in a few hours, and the mountains make wind and cloud hard to pin down. Our biggest snowfalls usually come with an east or northeast wind (“upslope”), sometimes when the forecast only hinted at it.
Chinooks can push the temperature up 15 to 20 degrees in a few hours, and the mountains make wind and cloud hard to pin down. Our biggest snowfalls usually come with an east or northeast wind (“upslope”), sometimes when the forecast only hinted at it.
Weather alerts: what the colours mean
Since November 2025, Environment Canada gives each watch, warning and advisory a colour based on how much impact is expected.
| Colour | What it means | What to do |
|---|---|---|
| Yellow | Hazardous weather that may cause damage, disruption or health effects. The most common alert. | Stay aware, adjust plans, check again later. |
| Orange | Severe weather likely to cause significant damage, disruption or danger, possibly for a few days. | Change plans, prepare your home and vehicle, check on others. |
| Red | Rare. Life-threatening weather with widespread impacts. | Act now. Follow instructions from officials. |
The type of alert still matters too:
- Special weather statement: a heads-up about something unusual. No colour.
- Advisory: a specific weather event that is less serious than a warning, such as fog or freezing drizzle.
- Watch: conditions are right for something dangerous to develop (for example a tornado or severe thunderstorm). Be ready.
- Warning: it’s happening or about to. Take action.
Get alerts on your phone
Install WeatherCAN and Alberta Emergency Alert. Phones in Canada also get the most serious alerts automatically, with a loud tone.
Install WeatherCAN and Alberta Emergency Alert. Phones in Canada also get the most serious alerts automatically, with a loud tone.
Using radar
- Play the loop. A single radar picture tells you little. Animate the last hour to see which way storms are moving and whether they’re growing.
- Colours show intensity. Blue and green are light. Yellow and orange are heavy. Red and purple in summer often mean hail and violent storms.
- Distance matters. The radar beam gets higher the farther it goes, so it can overshoot light snow and low cloud far from the radar site.
- Snow looks weaker than it is. Light blue on radar can still be heavy, blowing snow on the ground.
- Virga: in dry air, radar may show rain that evaporates before it reaches the ground.
- Clutter: near the radar, hills, buildings and even birds can show up as small fixed spots.
Summer storms grow fast
Thunderstorms on the prairies can go from a small cloud to hail in under an hour. If you see towering clouds building by early afternoon, check the radar often.
Thunderstorms on the prairies can go from a small cloud to hail in under an hour. If you see towering clouds building by early afternoon, check the radar often.
Rain and snow: rate vs. amount
The rate (millimetres per hour) tells you about flooding and driving. The amount tells you the total. 10 mm over a whole day is a gentle soak; 10 mm in 20 minutes floods streets.
- Lethbridge gets well under 400 mm of precipitation a year, so 25 mm in a day is a lot for us.
- As a rough guide, 1 cm of snow holds about 1 mm of water. Dry prairie snow can be much fluffier, so the same water can fall as 15 to 20 cm of light snow.
Watch the sky yourself
- Chinook arch: a clear band of sky over the mountains under a sheet of cloud. Warm, gusty west winds are coming.
- Towering cumulus by noon: thunderstorms are likely later in the day.
- Falling pressure and a wind shift: a change in the weather is on its way.
- Halo around the sun or moon: high cloud ahead of a system, often 12 to 24 hours before rain or snow.
See live readings from our West Lethbridge station, or try the cloud guide, hail and lightning tools.
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