"It was too cold this morning."
Translation:Roedd hi'n rhy oer y bore 'ma.
I believe that in certain occurrences of the soft mutation (so-called 'weak soft mutation'), rh and ll do NOT mutate. The mutation of feminine nouns after yr/y is one of these cases (y ferch but y llaw); mutation of nouns/adjectives after yn is another. In most cases though (eg after dwy/dau, after i etc) rh and ll are not excepted.