Well water temp up here is anywhere from 40-50 degrees right now just wondering if there is an optimal temp to start the topwaters?

I start catching bass on topwaters when the temps hit the mid 50s.

As a general rule I use topwaters for bass, smallies included, during morning and evenings and during cloudy weather. A few times during the day topwaters work as well, such as when bass are busting prey on top. When bass are holding on very shallow flats, buzzbaits can catch them all day at times.

Fifty degree water?  You must be on the Cape.  For smallies, start throwing topwaters in a few weeks.  Prespawn is the best time.  Throw them high so they make a splash, then just let it sit--sometimes a minute or more later they will attack.  Sometimes also on the first twitch.  Switch from poppers to walkers to props, etc.  They will go for different approaches on different days.

Don't rule out topwaters during the day, especially for smallmouth. Smallies seem more likely to hit topwaters in the middle of the day than largemouth. I've used topwaters in the middle of summer on bluebird days and done well in small rivers.

Don't rule out topwaters during the day, especially for smallmouth. Smallies seem more likely to hit topwaters in the middle of the day than largemouth. I've used topwaters in the middle of summer on bluebird days and done well in small rivers.

Agreed. Though MOST of my daytime topwater action is during cloudy skies, I have had days where topwaters worked and a couple where they were the bait of choice, even in 90 plus temperatures in bright blue skies. Smallmouth in rivers are also more likely to hit topwaters during the day for sure.