What I would really like to see is data going back say over the last 50 years showing the number of like 60+, 70+, 80+ days during the months of March, April, and May and see if there has been an increase in the number of days for these occurrences over the years (I think we know the answer to this but would be nice to see).
it seems no matter hat transpires over the course of the month...at the end of it we end up above-average in terms of temperatures. We probably could have gotten a 2' blizzard April 17 and below-average temperatures for 4-days centered around that date...and the month would still finish AN.
The thing is our warm days...seem to overperform and by several-pus degrees and of course we have nights where temperatures remain above-average (which this is what seems to be driving the AN times...warmer overnight lows as opposed to daytime highs). The only way we really hit climo is getting these below-average airmasses and we somehow still manage to spike to climo values.