2 years ago here in California, north of San Francisco 120 raven flying miles or so, 1800 feet elevation, 50 raven flying miles inland from the coast, on June 3rd it did a small flurries of snow.
Last year May 8th was a good start for the main garden.
This year mid april was, and peas went in day before st. patrick's day.
These polar cells and el ninos, and atmosphere rivers, weakening polar vortex doohickies, lots of these things are doing counterintuitive things. When there is less total deep ice in the arctic ocean the natural vortex above the north pole is not as strong, and the air up there has its moisture levels changing. So the arctic air mass slips south. Some of that directly cools areas, while other areas get temperate air moving north, which then cools up north. I was reading about this in Scientific American. So that chilled temperate air that moved north then comes back southward because the polar vortex that normally holds the polar air masses up there is still weakened because it is over cold water or thin ice instead of the deep normal arctic ice.
Meantime, don't let it fool you. Now is the time to invest in coastal Greenland real estate!!!