We are low here, in a river valley. In the wider surrounding area the temperature stayed above zero. At my place it dropped to between -0.5°C and 0°C, depending on the spot. This was from 5am to 6:30am.
Of course, the official measurement is at 2m height. How cold it got right down at ground level, I don’t know. We’ll find out in a few days.
All of it was sown at the end of March — by broadcasting, not with a planter.
Anyway, people around here say: if you plant early, you still have time to replant.