In general anything under 15 is no big deal. I've had my 40 size planes out in 25-30 & it gets pretty hairy on landings.
I think it also depends on how much the wind is gusting. For example if it's steady 20 MPH winds your landings will still be smooth at a walking pace, whereas if it's gusting you'll have almost no ground speed so if the wind dies down you'll stall.

I think it depends a lot on the size of your plane as well. If you've got a 50% then it will obviously handle a lot more wind than a small trainer.