I used to have a 19 foot sea ray. Anything up to 4 footers was ok. Past that no. Wind speed and direction... well if it's out of the south, it can be quite windy and you can still get out if you hug the shore and such, out to about a mile. If it's out of the north or NE or whatnot, usually about 15-20 mph will produce 4 foot waves.

Keep in mind too you don't want to go out if it's already at your limit just to have it kick up more.

I was out today. West winds swinging between SW and NW, about 15 mph. I'd say waves were about 3 feet. Maybe a few cresting to 4. Not whitecapping yet. That's another good indication; when you start to get the tiniest froth of white at the top of some waves, it's about the limit for a 20 foot boat- at least it was mine.

These days I am in a 24 foot hard top. I'll GO out in anything up to 5 footers, but I've gotten stuck in it with 8-9 footers... it was pretty damned miserable and had to chug in at about 4 mph, with some waves breaking over the nose faster than the boat would rise up over them.

This lake can kick up fast, no fish is worth your boat or your life.