Hormuz Tensions and Oil Price Surge: Why Did the U.S. Market Decline?

On August 31 in U.S. local time (early September 1 in Korea), New York markets all turned lower on the final day of a monthlong rally. The S&P 500 closed down 0.3% at 7686.14, the Dow fell 0.7% to 53185.90, and the Nasdaq dropped 0.1% to 26370.89. The small-cap–focused Russell 2000 also slipped 0.5%, marking a broad-based correction in risk assets.

The immediate catalyst was news that the U.S. carried out an airstrike on an Iranian rocket launch site near the Strait of Hormuz. Brent crude then surged 2.7% to $90.49 per barrel, reigniting concerns over rising energy costs that could fuel both inflation and Fed tightening risks. Energy stocks managed to hold ground—Exxon Mobil rose 2.7%, Chevron gained 2.1%—while most other sectors moved sharply lower.

In the bond market, the 10-year Treasury yield climbed to 4.75%, reclaiming levels last seen when the Trump administration hinted at intervening in the debt market. The 2-year yield similarly held around 4.34%, with markets still pricing in better than even odds of another rate hike. The hawkish tone from Fed Chair Powell’s post-Jackson Hole warning that “inflation remains too high” continued to weigh on sentiment today.

With no major economic releases scheduled, investors are now focused on this week’s employment data and next month’s inflation reports. In the meantime, company- and policy-specific headlines drove stock moves. Amazon slid 2.5% on reports that the Federal Trade Commission and over 20 state attorneys general are preparing a price-manipulation lawsuit. Edison International and PG&E plunged more than 20% amid heightened legislative risk tied to California wildfires, while GameStop climbed over 2% on better-than-expected Q2 guidance.

Ultimately, the August pullback laid bare the market’s recent vulnerability chain—resurfacing geopolitical risks → oil rebound → upward pressure on rates. Yet all three major indexes still finished August in positive territory, suggesting this was more a one-off adjustment to uncertainties around the Israel-Hamas war, oil, and Fed policy than a full trend reversal. For investors, the key will be how upcoming jobs and inflation data over the next few weeks reshape the Fed’s rate path and the outlook for oil prices.