CALGARYWEATHER.
Hailstorm Alley, chinooks, snow load, and what to do after a storm.
- GUIDES
- 4
- GLOSSARY TERMS
- 13
Calgary's weather is unusually hard on buildings. The city sits in Hailstorm Alley, one of the most active hail zones in Canada, chinooks can swing temperatures dramatically in a day, and spring snow comes heavy and wet. Each of those stresses a roof differently.
Understanding the weather doesn't stop it. It does help you choose materials, spot damage sooner, and act correctly in the first days after a storm, when most expensive mistakes get made.
- Why does Calgary get so much hail?
- What do chinooks do to a roof?
- How much snow can my roof carry?
- What should I do right after a hailstorm?
READ THEM IN THIS ORDER.
- 01The first 48 hours after a hailstormIn the first 48 hours after hail: stay off the roof, photograph soft metals, siding, screens and your car the same day, tell your insurer or broker and note the storm's date and time, cover anything broken and keep the receipts. Don't sign anything at the door before a proper inspection and your adjuster's visit.
- 02Calgary hail season explainedCalgary sits in Hailstorm Alley, the strip of Alberta where the Rockies help build tall, cold storm clouds, which makes it one of the most active hail zones in Canada. Hail season runs through the summer, usually peaking in July and continuing into August.
- 03Chinooks, freeze-thaw and your roofA chinook is a warm, gusty wind off the Rockies that can lift a Calgary winter day well above freezing within hours before winter comes back. Every thaw sends meltwater into seams and every freeze turns it back to ice, which loosens flashing and sealant, lifts brittle or unsealed shingles, and feeds ice dams at the eaves.
THE BASICS
Plain-language primers. Assume nothing.
Chinooks, freeze-thaw and your roof
A chinook is a warm, gusty wind off the Rockies that can lift a Calgary winter day well above freezing within hours before winter comes back. Every thaw sends meltwater into seams and every freeze turns it back to ice, which loosens flashing and sealant, lifts brittle or unsealed shingles, and feeds ice dams at the eaves.
The first 48 hours after a hailstorm
In the first 48 hours after hail: stay off the roof, photograph soft metals, siding, screens and your car the same day, tell your insurer or broker and note the storm's date and time, cover anything broken and keep the receipts. Don't sign anything at the door before a proper inspection and your adjuster's visit.
DEEP DIVES
For when you're mid-decision, mid-claim or mid-argument.
Calgary hail season explained
Calgary sits in Hailstorm Alley, the strip of Alberta where the Rockies help build tall, cold storm clouds, which makes it one of the most active hail zones in Canada. Hail season runs through the summer, usually peaking in July and continuing into August.
Snow load and wind on Calgary roofs
Calgary roofs are built to the snow load the National Building Code sets for the city, and most houses never need snow removed: weight matters more than depth, so clear only after unusually heavy, wet buildup, and from the ground. Wind damage starts at the edges, corners and ridges, where uplift is strongest and the shingle seal is weakest.
THE WEATHER & HAIL GLOSSARY.
- Chinook
- A warm, dry westerly wind that comes down the eastern slopes of the Rockies and can raise winter temperatures in southern Alberta quickly. The thaw and refreeze that follows is hard on roofs and eaves.
- Freeze-thaw cycle
- One round of water freezing and then thawing. Water expands as it freezes, so repeated cycles pry at cracks, seals and joints.
- Ground snow load
- The snow load on the ground that the building code starts from when working out roof snow loads, based on the snowpack expected to be exceeded only once in 50 years on average. It's written Ss and measured in kilopascals.
- Hail Alley
- Hailstorm Alley, the stretch of Alberta from around High River north toward Red Deer, one of the most active hail zones in Canada.
- Impact rating
- A class showing how a roofing product performed in a standard lab impact test, such as UL 2218 Class 1 to 4. It describes a test result, not a promise the roof won't be damaged by hail.
- Insured loss
- The part of the damage from an event that insurers pay on policies. Published storm totals, such as IBC's, count insured damage only, not uninsured losses.
- Kilopascal
- A unit of pressure, written kPa, that building codes use for snow and wind loads. One kilopascal is about 102 kilograms spread over each square metre, or roughly 21 pounds per square foot.
- Rain load
- The extra weight from rain soaking into snow on a roof, written Sr in the building code and added to the snow load.
- Snow load
- The weight of snow and ice on a roof. Building codes set the loads a roof must be designed to carry, based on local climate.
- Soft metals
- Thin metal items around a house that dent easily in hail, such as roof vents, chimney caps, meter covers, air conditioner fins and mailboxes. Photos of them help document a storm.
- Thermal cycling
- The repeated expanding and shrinking of building materials as temperatures change. Because metal, wood, asphalt and caulking move by different amounts, it strains flashing and sealants over time.
- Wind rating
- A class showing how a shingle performed in a standard wind test, such as ASTM D3161 or ASTM D7158. It describes a correctly installed, fully sealed shingle, so real roofs can lose shingles in gusts below it.
