Katherine's senior firefighter Bernie Welsford says at least half of the fires lit over the past few weeks were suspected of being ignited deliberately.

"Fires are not lighting themselves, animals don't go around with matches and we haven't had any storms," officer in charge Bernie Welsford said.

"We don't know when the next monsoonal rains will arrive, tie that with increasing temperatures, high winds, low humidity and 100 per cent curing rates - that is ideal for fires and makes it very hard to fight."

Overstretched and heavily reliant on volunteers, the fire brigade has spent the past couple of weeks reacting to fast moving grass fires in hard to access areas of Katherine.

"Last week we had three major fires that were lit deliberately," Mr Welsford said.

"We had a chopper doing an aerial survey over a fire at Zimin Drive and we saw seven points of ignition. If you get multiple points of ignition it is deliberate."

On Wednesday a fire at Stuart Estate had already blazed through three hectares of grass and shrub when Mr Welsford arrived, and in just ten minutes had spread to 20 hectares.

Crews from Darwin were called in to help manage the fire despite a pool of 20 volunteers.

"We only had three units, no-one else could get here. We had to go defensive and carry out back burning to protect assets," he said.

"At the same time a fire was started by someone at the research station. Bushfires NT had to send crews out to prevent the spreading.

"It puts not just the public at risk, but our lives too."

Fires have blackened bush lands and threatened properties across Katherine as the region struggles through an especially long and parched season.

The Northern Territory is experiencing its driest year for almost half a century, and the Bureau of Meteorology is predicting a late start to the wet season.

"These are the worst fire conditions I have seen in years," Mr Welsford said.

"Cure rates are at 100 per cent and we have very low relative humidity. The last week and a half we have seen 20-30kmph gusts of wind getting up to 40-50kmph."

Feburary, March and April was an especially busy time for the firefighters as they carried out strategic fuel reduction burns in preparation, but they are still dealing with properties marked as high risk.

"We are in a position of reaction, and we have done everything we can to make sure the town is protected," Mr Welsford said.

"Because of the weather conditions and fuel loading the fires have been more intense and difficult to control."

Authorities are warning residents to be prepared for more fires as scorching temperatures set in.

Residents, especially those living on large properties, must ensure firebreaks are a minimum of four metres wide and maintained.

Gardens should be cleared of debris and there should be clear access for fire trucks.

"Think before you act," Mr Welsford said.

"It only takes one little ember with these wind conditions to destroy thousands of hectares."

Igniting fires illegally can incur fines in the thousands.

"If you see anyone who might be lighting a fire or acting suspicious call 000 immediately."

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