The northern-most capital city collected a total of 623 millimetres, one-and-a-half times the long-term average, making it the wettest January in 12 years.

Sam Terry, meteorologist for Weatherzone said the active monsoon trough sitting across the Top End was the reason.

"The trough has been drawing in equatorial moisture, generating widespread rain and thunderstorms," he said.

"The monsoon trough is not an unusual feature in the Northern Territory at this time of year, but it can vary in its activeness and movement. This year it has been quite active."

The rainfall also managed to reach further south. Alice Springs recorded 141 millimetres for the whole month, the wettest January in nine years.

As well as the rain, Darwin has also just experienced its coolest January since 2006.

On the fourth of the month the temperature peaked at 28 degrees, four below the norm and the coolest January day in four years.

"The persistent rainfall and thick cloud cover really acted to prevent the sun from heating things up, hence the below average January temperatures," Terry said.

"However, it sounds more exciting than it is. There is not a lot of variability in the tropics, so a slight change like this can make records seem significant."