American drivers have crossed a grim threshold just as summer travel ramps up, with average gas prices topping $4 a gallon in all 50 states.

According to GasBuddy and AAA, as reported by Fortune, regular gasoline has now cleared $4 per gallon nationwide, with the U.S. average reaching $4.56 on May 20. That's up sharply from $3.14 a year earlier.

Georgia and Mississippi were the least expensive states at $4.01, while California was the highest at $6.15 per gallon.

Analysts say prices could climb even higher in the months ahead. GasBuddy projected a summer average near $4.80 a gallon from Memorial Day to Labor Day. If America's war with Iran keeps the Strait of Hormuz shut for much of the summer, the national average could top $5.

The price jump began in early March as the conflict disrupted crude flows through the strait, which is a major global shipping route. Heavier seasonal demand is also adding pressure.

In California, the shutdowns of the Phillips 66 Los Angeles refinery and Valero Energy's Benicia refinery have made an already tight market even more vulnerable.

Higher gas prices can ripple quickly through household budgets. Families planning vacations, commuters driving to work, and small businesses that depend on transportation all feel the squeeze when costs at the pump rise.

GasBuddy said summer road trip plans have fallen nearly 70% from last year, though 56% still expect to take at least one.

The spike is also a reminder of how deeply fossil fuels can destabilize daily life. Dependence on oil and gas leaves communities exposed to geopolitical shocks and price spikes, while pollution from the industry contributes to asthma, heart disease, cancer, and premature death.

Burning fossil fuels also worsens extreme weather disasters that can destroy homes, livelihoods, and local economies, even as many households continue paying high energy costs while corporate profits soar.

For California drivers, the pain is especially intense. The state's stricter fuel rules, limited pipeline access, and refinery closures mean it often must import more fuel from Asia, where supplies are also strained by dependence on Middle Eastern oil.

Fortune noted that Alaska, Hawaiʻi, Illinois, Nevada, Oregon, and Washington are also averaging above $5 a gallon.

Some states are already suspending gas taxes, and federal relief discussions are underway, Patrick De Haan, head of petroleum analysis at GasBuddy, told Fortune. While those measures may not solve the underlying problem, they could provide some short-term breathing room for drivers facing summer travel costs.

Longer term, the volatility is another argument for accelerating cleaner, more affordable transportation options that are less tied to oil markets. 

If you're in the market for a new car, consider switching to an EV. Even while fuel markets are stable, EV drivers see significant savings by ditching high prices at the pump and lower overall maintenance costs. 

"Americans are going to pay billions more to get where they're going this summer and, even after the strait reopens, it could take a year or more for gas prices to fully recover," De Haan said. "Every bit of relief matters."

Get TCD's free newsletters for easy tips, smart advice, and a chance to earn $5,000 toward home upgrades. To see more stories like this one, change your Google preferences here.