(Later, post cup of tea.) Usual advice — don’t plant till the soil is warm enough to sit on. Don’t rely on air temperature as the air is often balmy while the soil is still frigid enough to stunt roots into not growing till Christmas.
Mulch only after the soil has warmed up or to delay stuff like carrots, parsley, lettuces going to seed by keeping the soil around them cooler so the poor things don’t realise it’s spring.
And plant absolutely masses because you’ll never feel quite so absurdly ‘must be out and plant’ till NEXT spring and, anyway, large plantings are much easier to look after than small ones. It’s not much more work to water, mulch and feed a big plot than a small one, and it’s all too easy to neglect a small one. A giant vegie garden has too much time and sweat invested in it to ignore.