Local residents said the fire 10 years ago was worse. Fire and police gathered in Manuka St to evacuate people if necessary.
Police urge people in the area to be responsible and follow the directions of emergency services and motorists should avoid the area, if possible.
James Winfield said he was at work when he got a call from his partner alerting him to the fire in the trees above Ravensbourne.
"I thought she was just exaggerating but as I drove home it realised, it's a pretty big fire," he said.
"At the moment I think it's going to be all right, the wind's no good. But Hannah [Boreham, his partner] is pretty nervous."
Jo McCullough, of Timaru, said she spotted smoke from the blaze on the motorway about 3pm.
About 100 people have gathered at Opoho Park and near the Caledonian Ground to watch.
Rachel Neynens, of Dunedin, called emergency services after spotting the fire about 2.45pm.
"My boyfriend and I were on the athletics track getting ready to do some exercise and we saw some smoke.
"Initially I thought maybe someone was having a bonfire or doing a controlled burn but a few seconds later it was quite big and I saw flames licking a tree."