Significant temperature swings are pretty much normal here in north-central California in March/April, and again in September/October. In recent weeks I did a 5K in fairly warm weather, and then a couple of weeks later (last weekend) did an 8K in which the lasy mile and a half was steady rain. I've seen similar swings in late September, one year doing a half in mid-upper 70s, and in another year, doing a 5K, starting at 80F and finishing at 90F, with some doing the half finishing at >100F. Weather swings in spring and fall are ordinary/normal, here.
Are spring and fall weather patterns in the East Coast steady and stable?