Gasoline prices in Nova Scotia are expected to tumble overnight as the provincial regulator changes pump prices two days ahead of schedule.

In a rare move, the Nova Scotia Utility and Review Board is invoking an interrupter clause to reset gas prices at 12:01 a.m. Wednesday.

The board said the move was necessary because of "continuing significant shifts" in the market price of gas.

While the board didn't say whether the price will drop, CBC News predicts a decrease of about six cents a litre. That would put the price of self-service regular gas at $1.268 per litre in Halifax, down from $1.328.

Graham Conrad, the executive director of the Retail Gasoline Dealers Association of Nova Scotia, said he also expects the prices to fall.

"After that huge hike in Ontario and Quebec — which we did not experience here — prices have been coming down steadily right across the country," Conrad told CBC News.

"New Brunswick was faster than we were so my suspicion is that we will be seeing a fairly substantial reduction tomorrow."

The price of crude oil has dropped 16 per cent in two weeks.

Conrad said that while that's good news for consumers, the wild price changes hurt service stations.

"If you buy at one price and the retail price goes down, then obviously you're losing money on all the product that you've got on hand," he said.

The move comes a few days after P.E.I's Island Regulatory and Appeals Commission dropped gas prices in that province by 5.5 cents per litre. In New Brunswick, falling international oil prices triggered that province's interruption clause last week.

New Brunswick's regulated gas system orders that province's Energy and Utilities Board to assign the maximum price of gasoline every Thursday. However, if the cost of any of the regulated fuels drops by a specific amount, the interruption clause is triggered and the EUB must order prices lower.

In Nova Scotia, the price adjustment is left to the discretion of the utility and review board — something the NDP government said it may be ready to change.

"I don't have a timeline for you. It's just been something that's been just briefly discussed and we really haven't had a chance to kind of set up how we might do this, when and whatever but as soon as I get that nailed down, I'd be glad to let you know," said John MacDonell, minister of Service Nova Scotia.

MacDonell said any change in the system will come after a thorough review with public involvement.

The prices of gas and diesel in Nova Scotia are normally set every Friday.

The utility and review board said the price of diesel wasn't changing ahead of schedule because market changes were not significant enough.