"Mae hi'n dwym."
Very odd Is "dwym" a dialect word? It isn't in either of my dictionaries and I have only come across "poeth" for hot up to now.
It's definitely dialect to some degree because I would use "Poeth" for hot and "Cynnes" for warm.
Thanks ibischris. Daft of me to forget it was mutated. Even in its proper form though t's not in Y Geiriadur Mawr although it is in my learners' dictionary but described as South usage which would explain why I had not heard of it before.