In a snowy climate, autumn is often the easier window. After the thaw, the soil can stay wet for weeks, and broadforking wet soil does more harm than good because it smears and compacts instead of loosening.
The key either way is moisture. Squeeze a handful from a few inches down: if it crumbles, it's fine to work; if it forms a sticky ball, wait.
If you do it now, cover the bed afterwards with a good layer of mulch, leaves or compost rather than leaving it bare. Then the frost, worms and soil life keep working on it over winter, and in spring a quick pass, or sometimes none at all, is enough.