Calgary is a fair bit drier than Edmonton (326 mm average yearly rainfall vs 366 mm), with the vast majority of it falling in the late spring and early summer, while Edmonton's rain is very spread out in comparison. The Calgary aerials were all taken at different times, the first one in September, the second one in late October, and the last two on the same day in late September. All images on the stock aerial site have dates on the page. Calgary's extra green-ness in the pics is due to an above average rainy summer last year.
Btw, here's an awesome Edmonton shot, from late September 2013.
http://www.stockaerialphotos.com/-/galle...-11e2-8367-fbc1ddf8b129-edmonton-alberta