GPT Group's development manager Steven Turner said August's rainfall, which was more than double the total for the previous four months, meant there had been delays to works along Keira Street.

"We had a targeted date of September 26, but with the rain over the last two weeks it's had a significant impact on the external works in and around the centre," he said.

"We probably lost about one or two weeks on the project, so now we're looking at an opening date for some time around the second week in October."

The delayed works will also mean Keira Street will need to stay closed to traffic until after October 1, when it was due to reopen.

"We've always said we would try to open Keira Street as soon as we could, but it was one of the areas that was most affected by the rain," Mr Turner said.

"We've communicated that to tenants along the street and will come back to them when we have more certainty."

He said GPT was now working with NSW Roads and Maritime Services and Wollongong City Council to set a firm date for the road reopening.

Meantime, Wollongong councillors were told this week that Crown Street Mall works would be finished by the end of October "without fail" despite the heavy rain.

Director of infrastructure and works Mike Hyde said there had been delays, but the council was still intending to finish its $22 million refurbishment project on time.

"The rain has had, and is continuing to have, an impact on what we do and the guys are working around that," Mr Hyde said.

"But the contractor is moving heaven and earth to achieve that October 31 deadline."

He said "really, really bad weather" in the coming weeks could mean minor works would need to be completed after this date, but he was hopeful this could be avoided.

"One hundred per cent of the work we're doing is outside, so to not have us saying we are going to have a two-weeks delay is a major achievement."