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 hailstormA calm, ordered checklist for the two days after hail hits your house, so you protect your home and your claim without rushing into anything.
- 02Calgary hail season explainedWhy the foothills east of the Rockies build so many hailstorms, when the season peaks, how to read hail sizes, and what the big Calgary storms actually cost.
- 03Chinooks, freeze-thaw and your roofChinooks can turn a frozen day warm in minutes, then winter comes back. Here's what that back-and-forth does to a roof and what to watch for.
THE BASICS
Plain-language primers. Assume nothing.
Chinooks, freeze-thaw and your roof
Chinooks can turn a frozen day warm in minutes, then winter comes back. Here's what that back-and-forth does to a roof and what to watch for.
The first 48 hours after a hailstorm
A calm, ordered checklist for the two days after hail hits your house, so you protect your home and your claim without rushing into anything.
DEEP DIVES
For when you're mid-decision, mid-claim or mid-argument.
Calgary hail season explained
Why the foothills east of the Rockies build so many hailstorms, when the season peaks, how to read hail sizes, and what the big Calgary storms actually cost.
Snow load and wind on Calgary roofs
What the building code actually designs Calgary roofs to carry, why the kind of snow matters more than the depth, when clearing is worth it, and why wind damage starts at the edges.
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.