If not for springs, Katherine would have gone the way as Edith, Fergusson and other streams in the region and dried up.

Officially the Katherine River is 20 centimetres deep today and has been for a long time.

But that's how low the official instruments can go.

Veteran residents say the flows at Knotts Crossing and Low Level Weir have definitely slowed over the past few weeks.

With several months of the build up to go, and the Bureau of Meteorology forecasting a later than usual start to the wet season.

Katherine draws its drinking water still from the river during the build up, which is mixed with PFAS contaminated bore water and then cleaned.

This lack of supply is the reason the town remains on water restrictions into its third year.

The bureau today said a sharp increase in humidity and overnight temperatures, bubbly (convective cumulus) clouds and the return of thunderstorms signalled the start of the build-up.

Maximum temperatures in the Top End and Gregory District will reach near record for September by next weekend, hovering around 40C.

Katherine is tipped to have a run of three 39 degree days.

Dew point (measure of moisture in the air, ie humidity) is steadily increasing.

During the dry season, the dew point is around 15°C for much of the day, but during the build-up dew point is usually 20-25°C, leading to much sweatier weather conditions.

This year's build-up is expected to be hotter than average, with rainfall between October and December likely to be below average, the bureau said.

Below average rainfall will put increasing pressure on water storage for Darwin during the next few months - water levels are currently low due to the low rainfall last wet season.

Humidity returning to the Top End and weaker wind strengths are contributing to reduce the risk of fire weather, and bringing relief from the persistent fresh winds and Severe Fire Dangers impacting the Top End last week.

Dust storms were prominent last week reducing visibility at Alice Springs and Tennant Creek down to less than 100m.

A thick cloud band brought the first rain and thunderstorms for many months to the southern districts of the NT with the first rain for three months in Alice Springs today.

While you're with us, you can now receive updates straight to your inbox each Friday at 6am from the Katherine Times. To make sure you're up to date with all the news, sign up here.