Monarchs can withstand a little cooler temps than some other butterflies. When they're in Mexico for the winter, sometimes it can get fairly cold there.
I live in weatern Il. We usally see our 1st butterflies mid April. The earliest ones are cabbage whites, Red Admirals,and silver spotted skippers. Some times I've seen a tiger swallowtail early. This year I hope they'll be back earlier. I have seen the 1st 3 I mentioed but it rains so much. We'll get a couple of nice days then it's cold again. Ah spring in beautiful Il This is a Red Admeral on Pink Thrift..