I dont use avg monthly temps as good indicators of extreme heat, it's better to use extreme heatwaves.
March 1990 stands out to me as the hottest weather I've ever seen in March with 3 consecutive days of 85+ getting close to 90 during the middle of the month. Ditto for April 2002 when we hit 90+ three straight days and almost 4, and topped out at 96, matching a similar heatwave in April 1976 (but in 2002 the heat lasted all throughout the spring and summer and even into early fall.)