Gall tymheredd uchel iawn fod yn beryglus i bawb ond mae mwy o risg i bobl oedrannus, plant, pobl â phroblemau iechyd cronig a phobl agored i niwed a all ei chael yn anodd ymdopi yn y gwres.
Very high temperatures can be dangerous for everyone but elderly people, children, those with chronic health problems and vulnerable people who may struggle to keep cool are at a higher risk.