Monday's high was 30.7 degrees, according to the Bureau of Meteorology. It happens only once every 10 years, on average.

“In April, over the course of 10 years, on average one of those days is over 30 degrees,” meteorologist Craig Ryan said.

Last year, the highest April temperature was 24.5 degrees.

In 2016, an especially warm April, the temperature also topped 30, reaching 31.1 on April 6.

Prior to Monday's top, the maximum average temperature recorded at Canberra Airport this month was 28.5 degrees.

At night, temperatures are more in line with what we expect in April. The coldest night so far was Sunday, April 8 when the temperature fell to 5.9 degrees.

The long-term average low for April, back to 1939, is 6.6 degrees. The lowest temperature on record for April was -3.7 degrees, recorded on April 25 1999. So far this month, the average overnight low is 10.6 degrees.

This year's warm week is set to continue, with 31 degrees forecast for Wednesday.

Canberra's record April temperature was 32.6, recorded on April 4, 1986.

The Bureau of Meteorology said while it is unseasonably warm this week it did not expect the record to be broken.

“At this stage, it’s not expected to go back up after Friday but it’s hard to tell that far in the future. After tomorrow’s high, the likelihood is low that it will pick back up again,” Mr Ryan said.

“It’s because there’s been a constant band of high pressure funnelling to the north. It is expected to pass on Friday where it’s partly cloudy.”

Cold fronts moving through south-eastern Australia during Thursday and Friday were expected to bring milder weather to the capital by the weekend.

For Canberrans heading to the coast, Saturday's forecast high at Batemans Bay is 27 degrees and Sunday's maximum is forecast to reach 25 degrees.