Northumbria Police took to Twitter to remind dog owners to make sure pets have fresh air and water if they are in cars.
They say they have already received a number of calls from concerned animal lovers.
The RSPCA is also urging dog owners never to leave their pets unattended in parked cars as tomorrow's Bank Holiday Monday is set to be the hottest on record.
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It says it has seen a worrying increase in calls to it’s 24-hour emergency hotline with numbers last year about dogs overheating reaching nearly 8,000.
There were 93 from the Tyne and Wear area and 118 from Durham.
RSPCA dog welfare expert Lisa Hens said: “It’s so dangerous to leave your pet inside any hot environment whether it be a car, a conservatory or even a caravan.
"The temperature inside a car can soar to 47°C (117°F) within minutes, even when the outside temperature is just 22°C (72°F) and this can be fatal for a dog.
"Cars heat up very rapidly in hot – or even warm – weather. Air-conditioning can disguise the danger that a dog will face once the engine is turned off.
“We would simply ask dog owners never to leave their pet unattended in a parked or stationary vehicle and, if the weather is warm, to leave them at home where they can access cool, shady parts of the house and lots of water.”
Today is another dry, warm and sunny day with temperatures in the high teens and tomorrow is due to be even hotter.
The Met Office says there will be long spells of sunshine across the North East with a maximum temperature of 26 °C.
You can call the RSPCA’s 24-hour emergency cruelty line on 0300 1234 999 for advice but, if a dog is in danger dial 999.