at what mph do the winds at pymie create waves that would make the lake unkayakable? 

Depends on your kayaking skills and type of kayak.  
 
You can fish in pretty heavy waves with a wide, stable SOT kayak.  
 
I'd say a 20 mph wind would begin to be uncomfortable though....depending on direction and most times, you could launch and find a place to fish and be out of the heavy waves...
 
 

a step or 2 past beginner/novice
pretty stable
SIK
 
thanks for the heads up.  i was looking for a benchmark and 20mph (being "uncomfortable") sounds like a good place to start.  would be launching at the north end of the lake.
 
saturday they're calling for:
8am SW @ 8mph - figured that would be fine
noon W @ 15mph - starting to get concerned
2pm WNW @ 18mph - mid to upper teens was the main reason i asked the original question
 
i've waded up there when the waves are surfable but i've never taken note as to what mph the winds were to create those kind of waves.
 
thanks again

Heed what coldfront says.  As a long time boater on the north end, she can turn ugly...FAST!

thanks for the tips.  bailing on saturday.  winds in the mid to high teens and gusts in the mid to high 30's doesn't sound like fun in a kayak to me.
 
i've been up there wading with small waves one minute and got chased to the shore/woods the next by crashing waves that would not be doable in a kayak by any stretch of the imagination.