That’s such a heated shall we say and debated topic .....I think whatever the low water temp is in the winter at about 10 above it they are on the move or already in place to some degree .
Hormones, moon phase ,water conditions and other things have play in it as well
I am sure some shallow lakes warm daily enough after 4 or 5 days of sunshine and warm weather to get the ball rolling
Don’t know the answer to the exact temp as I never have figured it out ,but to be it’s time to poke around shallow some and make sure they are or ain’t there .....
Some lakes vary temps from way up creeks to the main lake almost 20 degrees as well