Canberra weather: Wet week ahead with up to 20mm of rain tipped for Wednesday

On Wednesday morning the Bureau of Meteorology downgraded its earlier forecast of up to 30 millimetres of rain for the day.

It also previously forecast up to 30 millimetres of showers from Thursday through to Monday, but on Wednesday morning halved that expected rainfall.

The Bureau's senior forecaster Rebecca Kamitakahara said not even one millimetre fell overnight on Tuesday, which was unexpected.

"The rainfall [forecast] amount may have changed slightly overnight," she said.

"We could have up to to five millimetres tomorrow, and it will be quite a windy day as well. Then on Friday and the weekend could see one or two showers about on each day but generally not looking like too much."

Winds of up to 30km/h on Wednesday and 45km/hr on Thursday were forecast for the capital.

On Tuesday, the Bureau's durty forecaster Andrew Haigh said the rainy weather was consistent with the seasonal outlook, which predicted a wetter-than-average spring, following Canberra's third wettest winter on record that was caused by a strong La Nina phenomenon.

Mr Haigh said the developing trough in Western NSW on Tuesday would combine with a cold air mass to make a fairly unstable atmosphere, delivering rain clouds on Wednesday.

"We also have quite a humid air mass in the upper atmosphere from the north-west. So that air mass is bring the required moisture to make the rain," he said.

"We also have generally northern winds keeping temperatures fairly mild to warm, and the high humidity keeps the temperature from falling down low."

Wednesday was expected to reach a top of 15 degrees, followed by a top of 13 on Thursday, 15 on Friday and 16 on Saturday.

However, the fairly strong winds could make Wednesday and Thursday feel slightly cooler.

Minimum night temperatures were forecast to stay between two and four degrees.