Tahoe can be pretty random. We have a lot of sunny days, and when the temperature is in the 30's and 40's and the sun comes out, it becomes "spring", even in mid-winter.
I skied Sugar Bowl and Squaw last week (Feb 6 and 7). I quit at about 2:00 both days because the snow became soft, slushy, and sticky in places.
That said, I agree with the above posts that conditions should generally be good until late March and then become spring-like (which is also good, just different good). But the emphasis is on the word "generally"; we can also have a cold storm in April.