The summer minimum is largely due to the development of a stable cell of high air pressure that develops to the southwest, this blocking high functions to move low pressure systems to the north, and the frequency of storm events in Vancouver during the summer is greatly reduced. Montreal is influenced by continental air masses from northern Canada and maritime air masses from the Atlantic. During the winter period, there is a high frequency of mid-latitude cyclones that produce considerable snowfall in the Montreal area. In the summer months there are many convective storms associated with warm, moist, unstable air masses. Total annual precipitation in the Arctic region is very low due largely to the low vapour holding capacity of cold air.
Warm air can hold much more water vapour before it becomes saturated and condensation occurs.
In addition, the Arctic is influenced by high air pressure and wind flow off the polar region for much of the year. Therefore Arctic region. Mild winter temperatures, mild but not warm summer temperatures, very high amounts of precipitation with summer minimum. Therefore Pacific region. Cool winter temperatures, warm summer temperatures, high amounts of precipitation.