S&P 500 slides 0.7% as oil spikes and megacap earnings disappoint

The S&P 500 slipped 0.7% this week, putting the index on track for a second straight weekly decline as oil prices jumped on rising U.S.–Iran tensions and earnings from Alphabet and Tesla disappointed investors【2】.

Market drivers

The immediate catalyst was a sharp rise in oil prices, which lifted energy‑related stocks but weighed on broader equity sentiment. The price surge is linked to heightened geopolitical risk between the United States and Iran, a factor that typically fuels commodity‑driven inflation concerns and can push risk‑off trading. At the same time, two of the market’s largest constituents reported earnings that missed expectations. Alphabet’s shares fell 7.1% on Thursday, marking its worst daily loss since May 7, 2025, while Tesla slumped 15%, its steepest one‑day drop since March 10, 2025【2】. The combined effect of higher energy costs and weaker megacap earnings pushed the S&P 500 into negative territory for the week.

Seasonal backdrop

Historical data adds a layer of context to the current pullback. Bank of America research shows that the three‑month period from August through October has been the weakest stretch for the S&P 500 since records began in 1928, with the index only up 55.1% of the time and delivering an average return of just 0.6% in September over the past two decades【2】. By contrast, the same calendar window historically favors gold, which has posted an average total return of 2.5% since 1992. These patterns support a defensive bias for the third quarter, according to BofA technical strategist Paul Ciana【2】.

What to watch

• Oil price trajectory – Continued spikes could deepen inflation worries and sustain market volatility.
• Upcoming earnings – Watch the next batch of large‑cap results, especially any that deviate sharply from consensus.
• Quarter‑end data – The end of the month will close the historically weak August‑October window; any reversal in trend could shift sentiment.

The S&P 500’s modest decline underscores how quickly external shocks—geopolitical tension, commodity price moves, and disappointing megacap earnings—can converge to test market resilience, especially during a historically soft seasonal window. The next few weeks will reveal whether the pullback deepens or stabilizes as investors digest these mixed signals.