The mercury at Canberra Airport dipped to a low of -4.5 degrees at 6.50am, colder than Thredbo's top station's overnight low of -1.9 degrees.

The morning was even icier at Goulburn Airport, with a minimum of -4.8 degrees just before 7am and a bone-chilling -6.4 at Cooma Airport shortly after 3.30am.

Peter Zmijewski, a senior forecaster with the Bureau of Meteorology, said Canberra's chilly morning was down to Sunday night's dry, clear conditions.

"Most of the time Thredbo would be colder than Canberra but there are occasions where it's the other way around," Mr Zmijewski said

"With a high-pressure ridge, what's happening is with radiation cooling a surface inversion forms and that helps actually in Canberra to achieve a lower temperature, in particular in conditions like last night with not much wind, not much cloud and quite dry."

After the cool start Canberra reached a top of 14.5 degrees on Monday shortly before 3pm.

Tuesday was expected to be the warmest day of the week with a maximum temperature of 16 degrees.

But overnight temperatures were tipped to remain low for much of the week.

Frost and fog patches were predicted across Canberra in the middle of the week, with predicted lows of -3 on Tuesday and Wednesday.

Thursday was expected to be slightly less chilly with an overnight low of -1 before the minimum temperatures began exceeding zero from Friday when a low of 4 degrees was predicted.

But the warmer overnight temperatures will have a downside, with clouds expected to gather on Friday leading to a high chance of showers heading into the weekend.