A HEATWAVE in Queensland has put 21 people in hospital. Ambulances were called to homes across the state's southeast as temperatures rose to 40C yesterday, an Emergency Management Queensland spokesman said. Twelve Brisbane residents and eight from other parts of the region were taken to hospital, none in a serious condition. Most of those affected were elderly, the spokesman said. Among those was a 70-year-old Brisbane man who succumbed to the heat while building a fence. Another elderly man from Woodridge, south of Brisbane, went outside his building when a fire alarm went off, the spokesman said. He said Queensland Fire and Rescue officers noticed the man was suffering with the heat and took the man back in before calling an ambulance. The bureau of meteorology said the temperature reached 40C about 2.40pm (AEST) yesterday before a cold front moved in. A much milder maximum of 29C was forecast for today.