At least half of the average November rainfall could fall across Canberra on Monday, the weather bureau has forecast.
And those who walk or cycle to work may want to reconsider; the bureau has predicted steady rainfall and thunderstorms throughout the morning.
Bureau of Meteorology duty forecaster Rob Taggart said there was a reasonable chance the rainfall on Monday would exceed half the November average, which at Canberra Airport was 64mm.
About 30 to 45mm is forecast.
Mr Taggart said that amount of rain was a once in every two years event.
“They’re not common events in November,” he said. “Every second November there may be a day where the airport gets more than 25mm.”
The forecaster said that most significantly the bureau had predicted “very steady” rainfall in the morning and a chance of thunderstorms.
“Hopefully it won’t be too early, and wake people up,” he said.
Mr Taggart said the rain would be easing to showers in the afternoon.
The rain is a result of a low pressure system entering the far northwest of NSW on Sunday afternoon and tracking southeast over the following 12 hours.
Mr Taggart said the system would pass over Canberra in the morning before ending up at the coast.
Monday could also be a lightly windy day, with winds of up to 30km/h predicted in the evening.
For Melbourne Cup day, the bureau forecasts a partly cloudy with a slight chance of a shower in the afternoon and evening.
The rest of the week looks drier, until the chance of more rain returns for the weekend.