The Alberta Ministry of Transportation offers a subscription service on its website to drivers who wish to stay up-to-date with road ban orders and seasonal weight changes. According to the website, seasonal weights for heavy haul are set according to the following schedule:
Spring: weather dependent, subject to thaw depth readings and begins at same time as Period 1 (weather dependent, subject to thaw readings of at last 25 cm.
Post-Thaw: June 16 (may begin one week earlier or one week later)
Summer: July 1
Fall: September 1
Winter: weather dependent, subject to frost depth readings of one meter or more. In winter, trucking weights can be greater because the pavement is less vulnerable when the ground beneath it is frozen, providing support.
Alberta also publishes a "Road Ban List" of major highways. Typically, the document lists weight restrictions of 90% of 75% of permitted axel weights. Access to the bans list (a PDF file) can be accessed from: http://www.transportation.alberta.ca/522.htm.
Current frost or thaw line:
Thaw/Contour Map (pdf)Calculate Oversize/Overweight Load Regulations and Prices Instantly with Oversize.io