The average cost of a gallon of gasoline in the United States reached $4.18 on Tuesday, climbing nearly 7 cents overnight. Prices have risen by $1.20 a gallon since Feb. 28, when Israel and the U.S. attacked Iran.

By the start of April, the national average for a regular gallon of unleaded had surpassed $4, hitting $4.17 on April 9. Gasoline prices increased by over $1 in one month between early March and early April. The Iran conflict has raised U.S. gas prices by $1 per gallon.

Crude oil, which accounts for 51% of the cost of a gallon of gas, continued to climb. As of Tuesday morning, Brent was trading around $111 a barrel, while West Texas Intermediate was just below $100 a barrel.

The U.S. and Iran agreed to a two-week ceasefire on April 8, which President Trump later extended. Trump met with his national security team to discuss a proposal from Iran that would allow for the reopening of the Strait of Hormuz but delay nuclear negotiations, White House press secretary Karoline Leavitt said. She said the administration was not necessarily considering the Iranian proposal.

"The Strait [of Hormuz] is not reopened — there's no cohesive plan for reopening it — and now negotiations have been basically stopped. So oil's been slowly recapturing some of what it gave up after the ceasefire was announced," said Patrick De Haan, a petroleum expert at GasBuddy.

De Haan said residents in Michigan, Wisconsin, Illinois, and Indiana could see a particularly large increase at the pump due to local refinery issues, including a power outage at a Northwest Indiana facility and a snag at an Illinois plant. Those issues have pushed wholesale gas prices up by approximately 40 to 50 cents from their high on April 7.

Even if shipping lanes fully reopen tomorrow, it will take weeks for oil tankers to reach their destinations, and it will take years to repair damaged oil production capacity in Iran and other impacted Middle Eastern countries. Gas prices typically rise faster after crude oil prices increase than they fall when crude oil prices decrease.

"You can't just turn on the supply of oil and gasoline like a switch," said Neale Mahoney, an economics professor at Stanford University. Mahoney predicts gas prices will remain above $4 over the summer and then start to decline in the fall.

Americans have spent $150 more on gas over the last two months than they would have if prices had stayed below $3 a gallon, Mahoney said. He predicts Americans will spend roughly $800 more on gas by the end of the year than they would have if prices had followed their pre-war trajectory.

Median-earning two-driver households will spend $70 more per month on gasoline, equal to about 1% of their post-tax income. More than 18 million U.S. households in the lowest-earning income quintile will spend an extra 5% of their post-tax income on gasoline. "There's not really much opportunity for people right now to cut back," De Haan said.