I've seen 2 cms shut down Vancouver. 10 cms causes Calgary to slow down. They'll tell you it doesn't but watch the roads and you'll see a drop off of about 80% of traffic.
Around here, 40 cm would likely close the airport and schools. Most non-essential governments offices would close. 50/50 chance of Metro Transit shutting down, most retailers would call off 30-50% of staff and most offices would tell people to work from home, if possible. That's pretty much a shutdown.
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