Canberra had just five millimetres of rainfall last month, its fifth driest January on record and 53 millimetres below the average rainfall for the month.

Water carter Peter Crowe said he had been on the road seven days a week, sometimes well into the evening, supplying property owners near places like Boorowa, Bywong and Jugiong.

''The last two summers have been wet summers and I think it's crept up on a lot of people. They weren't expecting to be running out of water,'' he said.

Water carriers or carters deliver water to areas around the Canberra region that aren't connected to the ActewAGL water network, such as Murrumbateman, Royalla, Tharwa and Braidwood.

They have also been the sole supplier of water to farms as tanks or bores ran dry in January.

Mr Crowe started his water carting business out of necessity, when he ran out of water on his property eight years ago during the last drought.

''I ran out at the beginning of the drought and I was told it was a 3½-week wait for water. That's when I went and bought the truck,'' he said.

Temperatures in January were well above average with a mean temperature of 31.6 degrees.

Temperatures stayed high on Sunday, peaking at a maximum of 39.3 degrees, and another day above 37 degrees is forecast for Monday.

AAA All Areas Water Carrying has three water trucks that consistently supply the region seven days a week, often from 5am until 9pm.

Co-owner Leslea Gruber said this January was the busiest they had had in at least 10 years.

''Flat strapped. Business has been very busy, because of our low rainfall, but hopefully we'll get the rain in the near future,'' she said.

Ms Gruber's business is the largest such service in the ACT and has been in operation for 28 years.

She said in one day her company might supply as much as 210,000 litres of water to rural Canberrans.

Farmer James Bingley, who runs a carting company with his brother as a side business during summer.

But despite the lack of rainfall, he said he would not be changing his schedule to take advantage of the surge in demand.

''This is the time we sheer every year, so that's what it is,'' he said. ''That's our income for the year.''