South Western Ambulance Service Trust has issued an appeal to the public after recording their second busiest day on record over the weekend.
The service said that it had experienced an unprecedented high-level of demand over recent weeks.
That demand then reached its second highest point on Saturday 17 July as thousands of people enjoyed the warm weather across the West Country.
South West Ambulance Service NHS Foundation Trust's Assistant Director of Operations William Lee asked the public to only call 999 in a "genuine, life-threatening emergency".
He said that people calling 999 and asking for ETAs had also been adding unnecessary pressure on the service.
"Only call 999 in genuine, life-threatening emergency," he said.
"Please don’t call us back on 999 for an estimated time of arrival [ETA] as we will not be able to provide one. Calling back for ETAs means that people who need immediate, lifesaving instructions cannot get through.
"Please do call us back in you no longer need our help or the patient’s condition worsens.
"If you’re out in the sun, please stay hydrated, stay in the shade and look after each other."