Nicola lake has a very predictable thermal and is quite a nice spot to ride. It's thermal is more than just "is is sunny?" though, you have to check the gradient going up the valley for increasing temps and decreasing pressures: https://wtfbc.ca/temp.php?station=BC/s0 ... C/s0000568
I've winged around Penticton a few times. Thermals blow from the north on warm days and can work on South end of Okanagan Lake or choke point around Sunderland, but pretty light, I was on 6m and worked one day. Otherwise, there's a rotary beach in Kelowna kiters go I think. During storm/wind fronts, nice South winds pick up. I've had luck North end of Skaha and naramata area. I've managed one day of foiling each of probably 4 visits the last few years.