The £21m road, which will link the west and east of the town, was supposed to be finished by March.
However, last winter's heavy rain meant contractors could not start building a bridge over the River Tone and the Bridgwater and Taunton Canal.
Richard Needs, from Somerset County Council, said it had also encountered other challenges during the project.
He said work to lift an existing bridge over Station Road had to be delayed as workers had found the ground conditions softer than expected.
"It's not a question of moving the bridge, it's working out what are the best foundations for the new bridge to be," Mr Needs said.
"As with all construction projects there are very difficult times and there are happy times... it changes from day-to-day but overall we're making good progress and we're getting there eventually."
The one-mile-long (1.6km) road is designed to divert traffic around the north of the town and will run from Priory Bridge Road, over the river and canal, alongside the railway to Staplegrove Road.
It is hoped the new road will divert traffic away from the town centre and Priorswood Road and help with the regeneration of the Firepool area.

The council said a decision would be made on the Princes Jetty location on Princes Parade after a feasibility study later this year.
Plans for a terminal in the Cunard Building were scrapped in 2014, because of an estimated cost of up to Â£15m.
The city last hosted regular transatlantic crossings in 1968.
An existing terminal at Princes Parade is estimated to have generated Â£7m for the Liverpool economy last year, the council said.
Liverpool Mayor Joe Anderson said: "The temporary cruise liner building has been a tremendous success and served us well, but a city of Liverpool's standing and ambition needs a permanent building if we are to continue the growth we've seen in recent years."
He added the cost of any development at Princes Jetty would be offset by the passengers' economic impact.
But he stressed there was "lots of work to do before we can give any scheme the green light".
A council spokesman said there had been "a doubling in the number of vessels visiting Liverpool" - from 31 to 61 - since they were able to turn around in the city's waters in 2012.
"Passenger numbers are up from 38,656 four years ago to an expected 86,365 this year."
The council has commissioned a study "into the design and cost of constructing a terminal capable of handling 3,600 embarking and disembarking passengers with baggage - twice as many as the existing facility", he added.
Cunard director Angus Struthers said it would examine if it could "incorporate Liverpool into Queen Mary 2's iconic transatlantic crossings" if the terminal plans are approved.
Liverpool hosted the headquarters of Cunard from its launch in 1840 until the 1960s, when it moved to Southampton.
A final decision is expected to be taken later this year.

The 38-year-old former Scotland and British and Irish Lions lock will work as a "resource coach".
He will add expertise in the area of line-out play, while supporting the development of younger forwards.
Meanwhile, scrum coach Massimo Cuttitta has left for personal reasons after almost six years with Scotland.
Capped 77 times, Hines announced his retirement from international rugby following the 2011 World Cup.
He will help the squad prepare for this year's tournament before broadening his role to include pro teams Edinburgh and Glasgow, the newly-established academies and international age-grade teams.
"This is a fantastic opportunity to help a team I played with for 11 years," said Hines, a Heineken Cup winner with Leinster in 2011.
"I think that Scotland have got some exceptional young players and I'm relishing the opportunity to help make them better than they already are.
"They've got huge potential and I want to help them in their development."
Hines played under Scotland head coach Vern Cotter at Clermont Auvergne and is pleased to be linking up with the New Zealander again.
"The chance to work with Vern again is another great benefit of this role," he added.
"He knows how I work and I know how he works, which might have been part of the decision why he asked me to come on board. We got on really well at Clermont.
"Part of helping the team mature is sharing my experience and showing them how not to make the same mistakes I did, on my travels, and in my 11 years playing for Scotland."
The completion date for a new road in Taunton has been delayed.
[NEXT_CONCEPT]
Liverpool has identified the preferred site of a proposed permanent cruise terminal that could see transatlantic crossings return to the city.
[NEXT_CONCEPT]
Nathan Hines is to join the Scotland coaching staff after deciding to retire at the end of the season, midway through a two-year deal with Sale.