I wouldn't bet that a summer of heat waves will result in such a change. Maybe after a winter of heatwaves...
More likely snow in the summer and failed harvests. Or a sudden shutdown of the thermohaline circulation. That could wake some people.
In India this summer was really cold compared to previous years. normally the temperatures hover around 45C but this time it barely went above 40C. And it even rained all over the place in summer. Not sure if this was some freak incident or is it related to ENSO(El nino southern oscillations) though. can't find enough information on the topic.
More people will buy air conditioners and will increase electricity demand, that will be satisfied by burning coal and gas