What Is 'Red September'? Bitcoin's Curse, and Why Wall Street Has the Same One

In brief

• Bitcoin has closed 8 of the last 13 Septembers in the red, averaging a 2.97% loss, the worst month of the year by both average and median return.
• September 2025 broke the streak with a 5.16% gain, Bitcoin's third straight green close, only for October to turn negative for the first time since 2018 days before a Trump tariff threat triggered $19 billion in liquidations.
• Bitcoin opens September 2026 around $77,500 after a near 25% jump in August, with the Fed weighing its first hike since 2023 and a midterm election year stacking its own seasonal drag on top.

Bitcoin investors have lost money in eight of the last 13 Septembers. The S&P 500 has averaged a loss in September since 1945, and researchers at Yardeni have traced the pattern all the way back to 1928.

Bitcoin didn't invent this curse, but still the digital asset has joined it.

Crypto traders call it "Red September," a cyclical market boogeyman of sorts that resurfaces every year right around now. But it isn't superstition. It's a data pattern stubborn enough that both a fifteen-year-old asset and a hundred-year-old stock index can't shake it.

But why though?

The math behind the curse

Since 2013, Bitcoin has closed September lower eight times out of 13 completed years, a 38.5% win rate, according to monthly return data tracked by CoinGlass. The average return is negative 2.97%, the median is negative 2.44%, and both numbers matter here: a negative median means even a "normal" September loses money, not just a couple of catastrophic ones dragging the average down.