Back in the days when I was teaching, my trips to Mexico were usually taken during summer vacation. My students would often ask me, "Isn't it awfully hot there in the summer?" I would answer, "No, I go down there to escape the hot Ohio summers." In Mexico temperature is determined by the altitude of the location. So, in spite of its tropical latitude, places in the central highlands of Mexico are quite pleasant. I can even remember a few times in August when I slept under a wool blanket.
Generally, in Mexico City, the hottest months are April and May. Winter is over, but the rainy season, which begins in June, has not yet arrived to cool things down. During the spring, the high temperature can get up to the low to mid-eighties.
However, we are having a heat wave right now in Mexico City, and the forecast looks like it will be unusually hot next week.
The rainy season has begun, although the rains have not been daily. Last night we had a very heavy thunderstorm. In spite of the rain, the high temperature has been over 80 F every day since my arrival. The average high for the month of June is 77 F. Next week we are supposed to have no rain and five days straight with a high of 89 F. I don't ever remember it being that hot in Mexico City!