Weather Conditions in Banff National Park in mid May?

You probably know that Alberta weather is completely unpredictable. Ski/snowboard season is over at the end of April/May. I go to Banff all the time, and I am planning my last snowboard trip next week. I live about 30 minutes from Banff. The snow will probably be gone by May. The weather is usually cool, but I doubt it would be very cold. Every time I have gone hiking in the mountains in May I am good with some pants and a sweater. It's possible for the trails to be icy since the sun does not go through the trees as easily. As for the water, I really have no idea. Some days the lakes look green, while other days they are bright blue, dark blue, or a dark ugly colour. I have rarely seen the lakes that turquoise colour, but when they are, the weather is nice and warm.