Call handlers received 906 calls for emergency assistance across the two counties between 00.01am on Monday, July 18, and 2.30pm on Tuesday, July 19.
The average number of 999 calls received in a 24-hour period is 110, according to Derbyshire Fire and Rescue Service.
At one point, calls were being diverted to Tyne and Wear Fire and Rescue Service due to the high demand.
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Group Manager Nathan Stevens said: “While our firefighters dealing with incidents are visible to the public, our 999 emergency control room operators often go unseen, yet do a vital job during any incident.
"The heatwave has caused a significant increase in the number of emergency calls they have handled for Derbyshire and Nottinghamshire.
“At around 11:00 hours this morning (Tuesday) the call volume was so significant that we had to call on our pre-arranged buddy fire and rescue service, Tyne and Wear, to support us with our call handling due to a fire on the embankment of the M1 causing a significant spike in 999 calls.”
The service has been calling on the communities of Derbyshire to help prevent emergencies and keep safe during the heatwave.
On Monday Derbyshire firefighters attended 29 fires, the second highest daily total over the past decade – 23 of these were fires in the open.
And on Tuesday, firefighters dealt with at least 12 fires in the open.
Group Manager Stevens added: “While the high temperatures are predicted to fall over the next few days, conditions will still be warm and grassland and open areas will still be tinder dry.
"We therefore need people to continue to help us prevent wildfires, taking a common-sense approach to not having garden fires, not taking BBQs into open areas, and ensuring cigarettes and glass bottles are disposed of responsibly.
“I would also like to remind people about the dangers of open water. With the Schools due to break up, we are asking parents and guardians to ensure young people know that cold water shock and hidden dangers can cause drowning in even the strongest swimmers, and to ensure they know how to float to live if they did find themselves in difficulty.”