Weekend heat wave a challenge for London Zoo's penguins
5 July 2013 Last updated at 15:22 BST
Many parts of the UK are expecting their hottest day of the year so far - with forecasters predicting the highest temperatures will be in the south-east of England.
Thermometers are set to rise to 26C in some parts, with warmer weather predicted over the weekend.
Richard Lister reports on how London Zoo's penguins are coping this the sudden burst of sunshine.