More than 300 Melburnians have fainted, collapsed or suffered heat stress since Melbourne's autumn heatwave hit four days ago. The Bureau of Meteorology has forecast a top of 39 degrees in the city today. At 1.48pm this afternoon, the temperature peaked to 37.3 degrees, after a low of 20.9 degrees at 7.02am, according to the bureau's latest weather observations. Metropolitan Ambulance Service acting paramedic team manager Susie Dean said the service had recorded more than 300 calls for fainting or collapse over the past four days, but they may or may not be related to the heat. There were another 15 calls for heat stress in the past four days. That was about 60 calls more than for a four-day period in February, when temperatures were lower, she said. Ms Dean said the number of heat stress calls was unusual for this time of year. ''Over December and January, it's more common to go to heat stress, but it's not a frequent call that we get,'' she said. ''Fifteen over four days is a lot higher than normal for us.'' During the heatwave, she said it was important to stay out of the heat, drink plenty of water, dress appropriately for conditions and exercise later in the day. ''People tend to be doing the right thing. They are coping quite well,'' she said. Scorching conditions are also being experienced in Adelaide today, with a forecast top of 39 degrees