Jashore had the previous highest temperature of the season at 42.6C
The deceased are 'Ujjal', 20, his brother-in-law 'Shahin', 30, and Siddique Hossain, 25.
Police say a bus and an autorickshaw collided head-on near the Sayedabaad bridge at the Sadar Upazila around noon, killing autorickshaw driver Ujjal and Shahin on the spot.
Bangabandhu Bridge's Paschimparh Police Station OC Aminul Islam said three autorickshaw passengers, who were injured in the accident, had been hospitalised.
Meanwhile, another autorickshaw and a four-wheeler collided at Ullaparha Upazila's Koyda Bazar area.
Ullaparha police OC Tajul Huda said a four-wheeler passenger Siddique Hossain was killed on spot and three others were injured.
The injured have been taken to a local health complex, he said.