Summer tends to be warm and sunny but winter can be very cold indeed, especially further north. In some particularly bad areas of the Rockies snow and ice can build up rapidly preventing road crew from keeping up with road cleaning and snow can accumulate to several centimetres. When driving during these conditions you will be required to use winter tyres or snow chains on your tyres. In fact any road in Canada can suffer from this condition during the numerous winter storms but the Rocky Mountains are particularly unpredictable from September to May.