Filling up on Key Biscayne now costs $5.79 a gallon for regular gasoline, the highest price in Miami-Dade County according to GasBuddy, and a 30-cent jump from just one week earlier.

The fuel-tracking site's weekly survey of 1,690 Miami-area stations, published Monday, found the island's price sits $2.36 above the cheapest station in Miami, which was selling regular for $3.43 on Sunday. The countywide average crossed $4 per gallon, rising 3.7 cents in a single week.

Key Biscayne has only two gas stations, both located near the Village entrance on Crandon Boulevard. With no competition deeper into the island, residents who don't fill up on the mainland before crossing the Rickenbacker Causeway face the county's steepest prices by a wide margin.

Three straight weeks of increases

Miami's average gas price has climbed for three consecutive weeks. Prices are 15.5 cents per gallon higher than a month ago and 91 cents higher than a year ago, according to GasBuddy data.

A week ago, Key Biscayne's two stations were both charging $5.49 per gallon. The 30-cent weekly increase on the island outpaced the Miami metro average, which rose 4 cents over the same period.

Nationally, the average price of regular gasoline reached $4.06 per gallon to start the final workweek of July, up 10.8 cents from the prior week.

Analyst: international conflict driving spike

Patrick De Haan, head of petroleum analysis at GasBuddy, attributed the surge to international conflict. "Average gasoline and diesel prices rose in nearly every state over the last week as continued escalations between the U.S. and Iran and renewed Houthi attacks in the Red Sea fueled concerns over global oil supplies," De Haan said Monday.

De Haan added that a weekend pullback in hostilities caused oil prices to open sharply lower on Sunday, suggesting the pace of pump-price increases may slow in the days ahead.

Island context

In the 1970s, Key Biscayne had seven gas stations spread along Crandon Boulevard. Fifty years later, only two remain. That limited supply gives island drivers few options and little leverage when wholesale costs rise.

Across Florida, the cheapest gas on Sunday was also $3.43 per gallon, the same as Miami's lowest. The most expensive in the state was $6.49, meaning Key Biscayne's $5.79 ranks near the top statewide as well.

What's next

GasBuddy publishes updated price data weekly. The next report is expected around Aug. 3.