WHAT a scorcher! Weymouth's waters were the hottest they've been for at least 20 years yesterday.

Official readings showed the temperature to be a tropical 19 degrees Celsius.

They were recorded by Department for Environment, Food and Rural Affairs temperature tester Peter Tambling.

Mr Tambling, who measures the temperature near the Pavilion every three days, said: "I was amazed. I was expecting it to be about 18. I've been doing this for 20 years in Weymouth and it's the highest ever. The previous best was 18.3 degrees last August."

The former Weymouth harbourmaster, 69, said he took the temperature at a depth of 4.5 metres, saying readings at shallower depths were inaccurate.

A Met Office spokesman said: "There is a trend at the moment. This reading is in line with other water temperatures we're getting in. In the middle of the Channel it's 17.1 degrees and off the Brest Peninsular it's 20 degrees.

"Apart from the sunshine, we believe it's being caused by a south-westerly wind bringing up waters from the coasts of north and west Africa."

He said British waters traditionally became even warmer in November. But while bathers were taking advantage of the hot spell, environmentalists were issuing warnings.

A spokesman for Greenpeace said: "The temperature rises are impacting on the entire marine food web.

"For example, phytoplankton, which feeds small crustaceans including krill, grow under sea ice. A reduction in sea ice implies a reduction in krill, which feeds many whale species, including the great whales.

"Whales and dolphins strand themselves in high temperatures. The great whales also risk losing their feeding grounds, in the Southern Ocean around Antarctica, because of the melting and collapse of ice shelves.

"Whole species of marine animals and fish are at risk due to the temperature rise - they simply cannot survive in warmer waters.

"Some penguin populations, for example, have decreased by 33 per cent in parts of Antarctica, because of habitat decline.

"An increasing occurrence of disease in marine animals is also linked to rising ocean temperatures."