Although the leaves are turning golden, Melbourne has so far escaped the winter blues, with the city in line to break a 42-year-old heat record.

The mercury has climbed to 20C or more for nine days in a row and could equal the 10-day, 1972 May record if the temperature reaches 20C as forecast on Tuesday.

Bureau of Meteorology senior forecaster Scott Williams said a slow-moving high pressure system in the Tasman Sea is responsible for the Indian summer, but a new record is not set in stone.

“It’s about 65 per cent probability that we will reach 20,” Mr Williams told AAP.

“There is cloud around, there is a little bit of rain around, so it’s no certainty.”

Despite the record warm spell, temperatures for May have only been 1.5 degrees above average.

Melbourne is expected to reach its maximum temperature in the early afternoon.