welcome to the forum. Kalwewa area is a very beautiful area indeed. but these days the lake is almost dried up...
and the warm air; sure you will get it, a lot...
. Pray for some rain before you go there.
Route : Take Colombo Kandy road (A1) > Turn left at Ambepussa and proceed along A6 passing Kurunegala > Turn left past Gelewela to B423 road and proceed along it.
all the best for your trip.