Montreal La Presse said Wednesday the premier is leaning toward calling an election that would be held Sept. 4.
That date holds a special significance for Charest — it is the 28th anniversary of his first election as an MP when Brian Mulroney's Conservative team stormed to power in 1984.
The scenario would involve Charest announcing the vote on Aug. 1 — a date that has already been set aside for the next cabinet meeting.
Marois told a news conference it would be "cynical" for the premier to launch a campaign smack in the middle of summer.
"This would deeply disappoint me," Marois said. "We know that half of Quebec is on vacation and isn't necessarily inclined to listen to what political parties have to say."
Charest was last elected in 2008 and has until December 2013 to call the vote.
But the Liberals have already made several campaign-style announcements in recent weeks and released new TV ads, including one that sniped at Marois for her support of Quebec's student protests.
The slow-motion ad showed the PQ leader awkwardly banging a pot at one of the demonstrations.
There was one clear indication on Wednesday that Charest could be planning a snap election.
Liberal stalwart Norman MacMillan held a news conference to announce he was quitting politics after a lengthy career.
MacMillan, who has sat in the legislature since 1989, acknowledged he was going to wait until later in the summer to make the announcement but that the Liberal party asked him to bring it forward.
Charest is not expected to have it easy in the election campaign.
Both he and his party are unpopular and are saddled with two ongoing controversies.
One is the lengthy dispute over hikes to university tuition fees and the other is the inquiry into corruption in the province's construction industry and into the awarding of public contracts.
The inquiry has already heard explosive testimony from a key witness who alleged that most political parties take money from construction firms. The probe is now on a summer break and resumes hearings in September.
The students, who have regularly turned out en masse in the streets to protest the hikes, have vowed to get involved in the election campaign and are planning strategy sessions during the next few weeks.