Though I have never collected sap, from those I know who did...

Not too late.
Temps 40F during the day, below freezing at night.
Best to ID while in leaf.
There's a reason they are called sugar maples
Tastes like syrup with 40x too much water in it.

tj

Thanks.. Any good books on that subject?

Joe

For Ohio, it's probably too late. Despite the cooler spring we've been experiencing, sap quality declines and becomes bitter later in the sap run. Best time for Ontario, Vermont, & Quebec can start in late February going to the beginning of April (subject to weather of course).
Further south, tapping trees becomes impractical because the best sap is quickly rendered bitter by the first warm spell (50+) even if temperatures cool down afterwards.