This summer was one of the 15 hottest ever recorded in Rochester history. In June, July and August, there were at least 9 days at or above 90 degrees. The rainfall was at an average for Rochester, but other surrounding counties saw less than normal levels.
It’s hard to pinpoint the reason for the high heat, its most likely due to natural variability but it does also match a larger trend of global warming due to an increase of greenhouse gasses over the last century.
If you plot the average temperatures of Rochester on a graph since the records began in 1926, there isn’t really a pattern there, but once you look at the data from 1976 and above, there is a clear upward trend in temperatures.