The council would likely advertise for candidate applications in February.
"January is a bit too soon, and people will be away."
He estimated the election, to be held by postal vote, would be held in April.
He said no one had approached him with plans to run, but he was sure there would be a few candidates.
Three out of the four highest polling at-large candidates who missed out on one of the four at-large seats in 2016 said they were seriously considering running in the by-election.
Contacted yesterday, Tony Christiansen, Mark Wassung and John Robson were interested in standing, while Matt Cowley had decided against it.
Christiansen, who was a Tauranga councillor from 2010 to 2013, missed out a seat to Rick Curach by 83 votes in 2016.
He said he still had plenty of passion for the city and was thinking about "giving it another go".
He said it was a shame ratepayers had to go to the significant expense and hassle of a by-election when the new candidate would serve only half a term.
"I would be happy to step into the position tomorrow."
Wassung, who polled sixth in 2016, said he was "seriously considering standing" as he felt there had been little traction on some of the issues he ran on.
Robson, who was elected in 2013 but polled eighth in 2016, said the "ridiculous" rates increases proposed for the next few years were among the issues motivating him to consider standing.
Seventh-placed Cowley said he would not run in the by-election.
"It's a good opportunity for another young person to put their hand up, and I would be quite happy to mentor them."
The by-election will overlap with the council's consulting the public on its draft budget for the next decade.
Brownless said he was not concerned about the impact a by-election could have on that process.
"It might be good actually, as it could focus people's attention on the long-term plan and consultation. It will give people an opportunity to say what they want to do or don't want to do."