I was reluctant to finish the forecast because of How April and May turned out. Cold nights cancelled out the warmth and then some, May 2015 was actually cooler than average in parts of the province. For summer I was not sure if the same was going to mean a cool summer(like in 2009 when there were plenty of 30°C+ days but cold nights removed any warm anomaly)
For example May 2015. High was ~18°C, low was ~2°C. The avg high is 17°C and low 4°C. The end result is a mean that is 0.5°C to 1.0°C below seasonal
June 2015 so far is about a degree above normal. The heat is turned up enough that the cooler nights due to the low humidity are not cancelling it out. This should be the case with the summer as a whole.
Overall Summer temperatures should be well above normal for almost the entire province. Meaning at least 2°C warmer than average. Though this translates to 3-5°C warmer highs and near to slightly warmer overnight lows. There will be plenty of 30C+ days throughout the province. The number of 35C days are also likely to be higher. July and August especially to be quite hot and there is a higher chance of summer heat dragging on well into September.
June 21-30: becoming hot and dry. Thunderstorms in northern Alberta, some severe. Potential of temperatures in the mid to upper 30s in parts of Southern Alberta
July: Very hot at times, very dry. Considerably more 30°C days compared to average. Higher chance of extremes(35°C+). Thunderstorms more likely to be severe even with lower frequency. High frequency of nocturnal thunderstorms. Best chance of cooler weather in mid month.
August: Hot and dry, Strings of 30°C days likely even for more central and northern parts of the province. High frequency of Nocturnal thunderstorms, some severe. Best chance of cooler weather mid to late month.
September 1-15th: Warm and very dry, hot at times. higher risk of dust storms.