Melburnians can expect the mercury to still be hovering about 30 degrees when they turn in.

A cool change won't arrive in until after midnight, bringing much-needed relief for restless sleepers.

The Bureau of Meteorology has forecast a top of 35 on Monday with scattered clouds. There is a slim chance of rain during the day, although it will only be a sprinkle at most, senior forecaster Scott Williams said.

The heat is going to hold up until about 8pm, when a small cool change will move through. That will bring the temperature down to about 30 degrees, Mr Williams said.

A second, much stronger system will roll through about 2am, with the temperature dropping quickly to about 19, where it will stay for the next few days. The second change should bring with it about 5 millimetres of rain, "enough to water the garden", Mr Williams said.

Tuesday is expected to be 22, Wednesday 23 and Thursday 24. Australia Day is expected to be fairly miserable, with a windy, drizzly top of 24.

The weekend looks nicer, with a sunny 28 forecast for Saturday.

Melbourne is experiencing a January "pretty much bang-on the long-term average", Mr Williams said.

Typically we get four or five days with nightly temperatures above 20 in January; this will be the third this year.

While temperatures are on average, Mr Williams said January had fluctuated significantly, with less consecutive hot days than usual.