A low of minus 5 degrees is forecast on Thursday, with a high-pressure system set to pass directly over the capital, bringing clear skies and light winds.

"Those [conditions] are very conducive to having the heat sucked right out," Bureau of Meteorology forecaster David Wilke said.

The cold snap should be short-lived, however, with the minimum temperature set to jump back up to zero on Friday, a day that should also bring 2 to 6 millimetres of rain and the hottest temperatures we've seen in nearly a month.

A top of 17 degrees is expected on Friday, which would make it the warmest day in Canberra since July 5, when it hit 18.2 degrees.

Mr Wilke said the long-term average top temperature for August at Canberra Airport was 13 degrees, making Friday's expected high 4 degrees warmer than usual.

However, the average low was 1 degree, meaning Thursday's predicted low was six degrees chillier than what forecasters had come to expect at this time of year.

"It's quite common that in a pattern where you get cooler temperatures, you also get warmer temperatures," Mr Wilke said.

"When there are clear skies, the sun is able to heat the Earth more efficiently, but it also cools down more at night.

"You do pay for it a bit with the mornings being so cold, but by the afternoon, it's a bit more tolerable."

In good news for people visiting the ski fields, 20 centimetres of fresh snow fell at Perisher overnight into Monday, while Thredbo received 15 centimetres.