Scorching summer days have stopped Whangarei's award-winning $32 million bridge from rising for boaties several times already this summer.
Whangarei District Council group manager infrastructure and services Simon Weston said the Te Matau a Pohe bridge had been unable to rise nine times so far this season, usually for about four hours often in the late afternoon or early evening.
The bridge has steel bascules that could jam if it is raised in temperatures over 26C.
"Only 2 per cent (9) out of 388 boats with tall masts have been delayed by bridge closures on very hot days this summer," Mr Weston said.
"Hundreds of other boats have been able to pass under the bridge while it has been closed. Yachties have been great to deal with and very understanding about the situation."
The council had been monitoring the steel expansion and has identified some minor work that should help reduce closures, he said. "We are planning to carry the work out in the next couple of weeks."
Council spokeswoman Ann Midson said the work would involve taking a thin slice of concrete off between the crash rail and footpath of the bridge.
"This won't affect the bridge structurally or its operation or reduce the bridge's durability."
In January last year, the council shaved off 30mm from the steel lip of the bascule, and lifted initial restrictions in March on the proviso it would continue to monitor the way the bridge responded to a range of conditions. In November, council had to reissue the warning when temperatures rose earlier than expected.
Whangarei temperatures in the past month have soared to 28C on some days, with MetService meteorologist John Law anticipating another five days of temperatures around 25C to 26C.
"Even through to Monday - after that there will be an the onset of sea breezes which will bring cooler temperatures."
On average, Whangarei has 18 days a year with temperatures above 26C and in the 2013 summer there were 19.