A combined force of 200 soldiers and firefighters are involved in efforts to contain the fires on the Pennine moors, but there are fresh concerns over their spreading.
About 80 firefighters worked through the night to prevent a grass fire spreading on Winter Hill, around 50km (30m) from the large blaze on Saddleworth Moor.
Greater Manchester Fire and Rescue Service (GMFRS) said that the new fire, along with that on the moor covering around seven square miles, meant they were "massively busy".
Scottish soldiers from the 100-strong A Company of the 4th Battalion, Royal Regiment of Scotland, known as the Highlanders, have joined more than 100 firefighters who have been battling the blaze since Sunday.
Major Phil Morgan, commanding the army detachment, said: "We meet every challenge and commit 100% in what we do.
"Currently we have broken our boys down into various locations and we are beating the fire with paddles and we are supporting them by moving equipment, we are putting water on the fires and we are doing everything we can to stop this fire at the moment."
Tony Hunter, assistant chief fire officer of GMFRS, said there had been a "significant effect" on the blaze in the past 24 hours.
"We have made significant improvements but I would put an air of caution there though, we had a similar occasion yesterday where we thought we were on top of it and it flared up."
Mr Hunter warned that while the fire was now "contained and under control", he said "things can develop" and if the wind blows the flames back on to the moors, it will act as a "fuel source" for the fire.
1:00He said the operation could last for weeks before the fire burns itself out, though the army deployment is for an initial 48 hours.
Mr Hunter said a "significant downpour of rain" would help – but none is forecast for days as the heatwave continues.
Pete Woodward, whose home backs on to the hills just 22 yards (20m) away, spent the night at his brother's home nearby after being evacuated on Tuesday evening.
Mr Woodward said: "I got back to the house last night to a towering inferno behind, very apocalyptic in view, and it was quite scary but exciting at the same time."
Dave Saxon, director of operations at Tameside Council, said the local authority was monitoring air quality, which had improved on Thursday, and there had as yet been no increase in GP appointments or attendance at A&E.
Fire chiefs say they are "not confident" of finding out how the fire began, given the size of the blaze, but there was no evidence it had been started by barbecues or off-road bikers.
Meanwhile, the UK enjoyed the hottest temperature of the year for the fourth day in a row on Thursday as the mercury soared to 33C (91.4F).
More from Greater Manchester
Porthmadog in Wales reached the sweltering high, beating successive highs since Monday.
The hot weather is expected to continue as temperatures are forecast to remain high into the weekend.
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