So glad this question was asked. Our weather here in Germany is also getting cooler for the week and next week too… from 0 (usually dropping to a few degrees below too) to 10 degrees.
My cucumbers have just germinated today after 3 days. Fortunately the courgettes and pumpkins haven´t yet!
I have been bringing my melon plants into a dark room in the nights as they have a hard time in single digits temperatures. I had them repotted a few weeks back so they aren’t terribly leggy anymore. Will likely bring the cucs into the dark room in the nights too.