“Sell in May and go away” — the oldest adage on Wall Street. Anyone who followed it in May 2026 missed one of the strongest months of the year. All three major U.S. indexes closed at all-time highs on Friday, May 29. The S&P 500 gained roughly 5% on the month, the Dow about 3%, and the tech-heavy Nasdaq jumped more than 8%. For the S&P 500, it was the ninth consecutive winning week.
And here lies the paradox that makes this month so fascinating and so dangerous: this record chase happened while inflation climbed to its highest level in nearly three years, long-term bond yields tested a 19-year high, and a war in the Middle East sent oil prices on a rollercoaster. Let’s break the month apart cleanly — what happened, why, and what it means for June.
The numbers: a month of records
Let’s start with Friday’s closing levels:
- S&P 500: 7,580.06 points (+0.22% Friday) — all-time high, +5% in May
- Dow Jones: 51,032.46 points (+0.72% Friday, +363 points) — all-time high, +3% in May
- Nasdaq Composite: 26,972.62 points (+0.20% Friday) — all-time high, +8% in May
The drivers on the final trading day tell the story of the whole month: IBM led the Dow at +12.9%, followed by Salesforce (+8.5%) and Microsoft (+5.5%). The losers were defensive and consumer-facing names like Walmart, Johnson & Johnson, and Nike. In other words: money flowed out of defensives into technology — the classic risk-on move.
What drove May: the AI machine
The engine of this month has a name: artificial intelligence. Practically every major move in May traces back to the AI infrastructure wave.
In the final week alone, this condensed into a barrage of headlines. Dell Technologies jumped about 33% on Friday — its best day on record — after the company raised its annual outlook to roughly $60 billion in AI server revenue. Snowflake had risen 25% days earlier, driven by a $6 billion chip deal with Amazon. And on May 28, Anthropic, maker of the Claude language model, closed a funding round valuing it at $965 billion — making it the world’s most valuable private technology company, ahead of OpenAI.
Perhaps the most spectacular single name of the month was Micron Technology. The memory-chip maker crossed the $1 trillion market-cap mark for the first time. In 2026 the stock has tripled; over the past twelve months it has eight-folded. UBS nearly tripled its price target, arguing the market still underestimates what AI means for the memory industry.
The secret winner: solar
While all eyes were on AI chips, a sector everyone had written off delivered the surprise of the month. Solar stocks posted their best month since September 2013. The Invesco Solar ETF rose roughly 26.5%. Individual names simply exploded: Enphase Energy gained over 110%, SolarEdge nearly 79%.
The reasons are a mix of factors. First, hope for falling rates, which makes the financing math for solar installations more attractive. Second, a genuine turnaround at SolarEdge, which expanded its margins for the sixth consecutive quarter and is approaching profitability. Third — and this is the elegant link to the AI theme — a new narrative: solar as a power source for the gigantic AI data centers that devour gigawatts of energy. On closer inspection, the AI boom and the solar boom are the same electricity bet.
The paradox: records despite hot inflation
Now to the real puzzle. How can the market celebrate all-time highs while inflation is rising?
On May 28, the PCE price index — the Fed’s preferred inflation gauge — showed an annual increase of 3.8%. That’s the highest level in nearly three years. At the same time, economic growth for the first quarter was revised down from 2.0% to 1.6%. Higher prices, slower growth — the specter of stagflation is knocking quietly.
Then there’s the bond market. The 30-year U.S. Treasury yielded over 5.1% at times during the month — the highest since around 2007. Normally this is poison for stocks, because bonds then become an attractive alternative. In May 2026, the market simply ignored it.
Why? Three explanations. First: corporate earnings were exceptionally strong — in the Q1 reporting season, 84% of S&P 500 companies beat expectations, the highest reading since 2021. Second: the AI growth story is so powerful it outshines all macro worries. Third: the easing in the Middle East. After Iran committed to normalizing shipping through the Strait of Hormuz, the oil price fell sharply — WTI crude slipped below $90. Cheaper oil means lower inflation in the future, and that’s exactly what the market is betting on.
What this means mathematically
Here it gets tricky. The S&P 500 currently trades at a forward P/E of around 21 — above the five-year average of about 20 and the ten-year average of roughly 19. So the market isn’t cheap. It’s pricing in strong future earnings growth — analysts expect full-year 2026 earnings to rise about 21%.
The problem with high valuations isn’t that they can’t rise further — they often do. The problem is they leave little buffer for disappointment. If AI demand stalls, if inflation sticks, if the Hormuz peace breaks, then bad news hits a market priced for perfection. That’s exactly what several strategists now warn about openly when they speak of “froth” in semiconductor valuations and remind us that bust cycles have historically followed booms.
Three scenarios for June
Scenario 1 — The rally continues (~45%): The Hormuz peace holds, oil stays low, inflation cools in the coming months, and the AI story carries. The first FOMC under new Fed chair Kevin Warsh on June 17-18 delivers no nasty surprises. The record chase rolls into summer.
Scenario 2 — Consolidation (~35%): After nine winning weeks, the market is technically overbought. A healthy breather of 3-5% would be normal and even healthy — it would build the base for the next leg up without breaking the trend.
Scenario 3 — The break (~20%): The Hormuz peace shatters, oil shoots back above $100, inflation sticks, and the June FOMC pivots hawkish. A market priced for perfection meets an uncomfortable reality. Correction across the chain, especially in the most expensive AI and chip names.
What smart money did in May
Institutional positioning remained remarkably cautious all month — an interesting contrast to the euphoria of the indexes. JPMorgan’s Jamie Dimon warned again and hinted the bank could spend up to $20 billion on an acquisition in the coming years — a sign he’d rather hoard cash for opportunities in a possible downturn. Experienced macro investors like Stanley Druckenmiller and David Tepper remain heavily positioned in energy. And Warren Buffett continues to sit on a 25-year record cash pile.
The pattern is consistent with what we observed all month: the most experienced hands in the business aren’t celebrating the records — they’re positioning for what comes after them.
What investors should concretely do
- Lock in gains without abandoning the trend: After +8% on the Nasdaq in a month, taking partial profits is legitimate — without fully exiting. Trends often run longer than you’d think.
- Check your concentration: A large part of May’s gains came from a handful of AI and chip names. Ask how heavily your portfolio depends on this one theme — and whether that’s intentional.
- Keep solar on the radar: The sector had its best month since 2013. After a 110% move in Enphase, the easy part is over — but the structural electricity thesis (AI needs energy) is intact long-term.
- Bonds are getting interesting: At over 5% on the long U.S. Treasury, you get real yield for the first time in nearly two decades. For the defensive part of a portfolio, that’s an argument.
- Mark the June FOMC on your calendar: June 17-18 is the first rate decision under Warsh. It’s the most important date of the coming month.
- Plan for taxes: Realized gains from U.S. stocks are subject to Austrian 27.5% capital gains tax. Anyone who profited heavily in May should factor in the tax burden.
The honest bottom line
May 2026 was an exceptional month — nine winning weeks, three indexes at all-time highs, a technological boom without equal. Anyone invested earned well. That’s the cheerful half of the truth.
The other half: this market isn’t rising because everything is fine. It’s rising despite rising inflation, despite high rates, despite a war. It’s rising because a single narrative — artificial intelligence — is strong enough to drown out every worry. As long as that narrative holds, the rally can continue. But a market resting on a single story is vulnerable the moment that story starts to wobble.
“Sell in May” was wrong this year. The more important question isn’t whether to sell in May, but whether you have the discipline not to get greedy after nine winning weeks. Records feel great — and that’s exactly the moment to stay sober.
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