Information regarding summer mountain conditions can be found on the Mountain Conditions Report, published by the Association of Canadian Mountain Guides.
Banff weather forecast. Yoho weather forecast
The summer snowpack exists in high alpine (above 3000m) and on glaciated areas, and consists mainly of well settled summer snow with the occasional dump of fresh snow and windslabs following a storm. Look for a solid overnight freeze for the best conditions, and avoid steep slopes when they're baking in the sun or soaked with rain.
During the first half of the summer, the high mountains are still shedding their winter snowpack and wet avalanches and cornice failures can be expected during the afternoons. Following a summer snowstorm, windslabs can also be expected during the immediate 24-48 hours following the storm.