Heatwave: 'Level 3 means take action'
Another large section of the country is now on heat wave watch with London and the south east joining the South West and Yorkshire and Humberside in being issued with a Level 3 alert by the Met Office.
The trigger conditions for a Level 3 are very specific - there has to be a 90% chance of heatwave conditions, when temperatures are high enough over threshold levels to have a significant effect on health on at least two consecutive days.
The reason for the alert system is to try and safeguard vulnerable people like children and the elderly.
Professor Virginia Murray, head of extreme events at Public Health England, told the Today programme's Evan Davis that "a Level 3 heatwave means that we have to take action".
She said that that the most important thing is to "drink lots of cool drinks" and to "look out for others".
Sally Colwill, manager of Chatsworth Care Home in Plymouth, said that the residents of the care home were suffering in the heat.
"The heat affects their breathing and they get panicy," she said.
First broadcast on BBC Radio 4's Today programme on Thursday 18 July 2013.
18 Jul 2013