Health authorities believe Victoria's record-breaking heatwave might have contributed to the deaths of about 374 people.

As temperatures soared between January 26 and February 1, so did the state's death toll with a 62% jump from the same time last year.

Victoria's chief health officer Dr John Carnie today revealed 980 people had died during the week compared to a mean of 606 deaths for the previous five years.

Most of those who died, 248 people, were aged 75 years or older with 46 people aged between 65 and 74.

Dr Carnie said it was not possible to say how many of the deaths had been brought forward by days or weeks because of the extreme heat.