I, too, saw a mourning cloak butterfly in the backyard, on Mar 18th and I have seen cabbage butterflies several times since then, during the hot weather.
I also saw a big soft light brown moth on a support for a streetlight - about 2 ' above the ground, at 4:00pm, in the heat of the day on Mar 22 or 23. Not really able to identify it, nor did I think of it as a dramatic first of the season, but of course it was one.