"Mother Nature has prolonged the winter and they've slowed down a bit," said Michael Coteau, minister responsible for the 2015 Games.
But taxpayers won't be on the hook for any overrun costs, he said, adding that he's confident all 31 Pan Am venues will be completed in time for the Games.
The setback is forcing the Tiger-Cats football team to use a smaller facility for their first two home games of the season.
The $145.7-million Tim Hortons Field was slated to open this month, a year before it was to host all 32 men's and women's soccer competitions during the Games.
Once completed, it will have 22,500 permanent seats and a potential capacity of 40,000 through temporary seating.
But the Ticats said they'll have to use Ron Joyce Stadium at McMaster University — which has 6,000 permanent seats and temporary seating for another 6,000 — for games scheduled this month.
The delay is unfortunate, but it will be short, said Infrastructure Minister Brad Duguid.
"The Hamilton Tiger-Cats will be running onto that brand new field at some point this summer — we expect by the third game — as soon as possible," he said in the legislature.
Disappointed fans should keep things in perspective, Coteau said.
"The fans are going to be really happy once the site is complete, because it's going to ignite the enthusiasm behind the sports team in Hamilton and across Ontario," he said.
The TO2015 organizing committee said they're still trying to get a final date for completion of the new stadium, but it will probably be August or September.
"I don't know anybody who's happy about the Hamilton situation," said CEO Saad Rafi. "I think we're all frustrated about that."
But Hamiltonians will have a world-class facility that's going to be around for the next 50 years, he added.
The CFL team spent the entirety of last season at the University of Guelph while the new stadium was under construction.
The residents in her hometown are frustrated with what appears to be a "lackadaisical" attitude towards getting the stadium ready in time for football season, said NDP Leader Andrea Horwath.
"The fans are the ones that suffer from not having the top-grade facilities and not having that ability to feel proud about the new stadium," said Horwath, who also represents the riding of Hamilton Centre.
It doesn't bode well for the government's ability to have the other Pan Am facilities ready on time either, she said.
"I think it's a bad omen for the Games overall that one of the major facilities has not been completed on time," said Horwath.
"And whether or not that's going to be a similar situation in other facilities — I guess it's wait and see."