The RSPCA is to prolong its long-running and successful campaign to warn people about the dangers of leaving pets to overheat in high temperatures.
The number of people prosecuted for heat-related pet-negligence fell to four last year, down from nine in 2001 and 15 the previous year.
An RSPCA spokesperson said: "The ongoing campaign is working, but, sadly, some people are still unaware or just don't take notice of our warnings.
"We received nine calls about pets suffering from heat distress last weekend."
Every summer, the charity sends posters and leaflets to veterinary surgeries and councils to warn people about the dangers of keeping animals locked in places such as cars and conservatories.
The charity also provides a list of precautionary measures to thousands of UK national and local print and broadcast media.
Advice includes telling owners to leave pets at home rather than in a car and reveals that the tips of cats' ears and noses are susceptible to sunburn.
The charity makes regular car park patrols to provide water to tied-up dogs.