The 65-year-old was cleared of eight other indecent assault charges by a jury at Manchester Minshull Street Crown Court.
He was accused of abusing four former pupils at Altrincham Grammar School in Greater Manchester and a fifth schoolboy from the Newcastle area.
Talbot was remanded in custody for sentencing on 13 March.
Judge Timothy Mort told Talbot, from Bowdon in Greater Manchester, his sentence should start immediately bearing in mind his "abuse of trust".
The Edinburgh-born former ITV star displayed no obvious reaction while the verdicts were read and nodded at the judge as he was taken down to the cells.
He had denied abusing boys aged 14 to 17, but was found guilty of two counts relating to former pupils at Altrincham Grammar School on canal boat trips.
The jury heard Talbot staged a naked orgy involving 10 drunken schoolboys on a canal barge.
He was said to have asked some of the pupils to pretend they were girls and lie on top of each other as photographs were taken.
One victim, who said he thought he was 14 at the time, said Talbot abused him after he was told to share a bed with him.
Another boy was abused on another barge trip in similar circumstances.
He said boys would take turns to sleep in Talbot's bed during the trip and when it was his turn Talbot "started talking to me about sexual stuff".
The incidents are said to have taken place on school trips in the 1970s.
It can now be reported that a number of similar complaints against Talbot have been passed by police to the Procurator Fiscal about alleged offences said to have been committed in Scotland.
Talbot was also questioned by Greater Manchester Police (GMP) about a serious sexual assault allegedly committed on a former pupil but the matter was withdrawn after the complainant died.
Talbot worked as a biology teacher at the boys' school until May 1984.
The court heard his teaching career came to "an abrupt end" following an indecent proposal he made to two pupils he invited to his home to look at his telescope.
The jury was told he was said to have been "obsessed" with teenage boys throughout his teaching career and "could not help himself" around them when under the influence of drink.
During the investigation, police seized a number of diaries Talbot kept during his teaching career.
Police found entries "highly suggestive of inappropriate behaviour".
Det Con Chris Doggart, of GMP, said: "Talbot was an extremely popular and well liked individual - both as a celebrity weatherman and formerly as a science teacher - who earned not only the trust and adulation of many of his peers and pupils, but also much of the nation.
"Now he has been exposed as an opportunistic sex offender and that reputation is rightly in tatters.
"Even when he was not committing offences against the two vulnerable young boys, his behaviour was wholly inappropriate and so far removed from his duty as a teacher to nurture and safeguard those under his care it really does defy belief."
The investigation was triggered in December 2012 following publicity into a separate historical abuse inquiry at another Altrincham school, St Ambrose College, which led to a nine-year jail term for ex-teacher Rev Alan Morris.
Nazir Afzal, chief prosecutor for the North West of England, said Talbot's offences were a "gross betrayal" of the trust placed in him.
"Parents and pupils saw him as a popular, likeable teacher who was willing to give up his time to take children away on school trips.
"In fact he used those situations as opportunities to sexually assault two teenage boys who should have been safe in his care."
In a statement, Altrincham Grammar School for Boys said: "These awful events took place over 30 years ago and naturally our thoughts go out to those former pupils who were subjected to this abuse.
"We are confident that our present pupils and their parents know that the school is totally committed to ensuring the safety of our students and staff at all times and that these historical offences have no bearing on the school's outstanding reputation today."
Talbot is best known for presenting the weather forecast on a floating map in Liverpool's Albert Dock for ITV's This Morning programme.
Ex-TV weatherman Fred Talbot has been found guilty of indecently assaulting two teenage boys when he was a teacher.