Bitcoin has again come up against statistics showing it has closed lower in September 8 times over the past 13 years, making it the weakest month of the year.

On Sept. 1, blockchain media outlet Decrypt reported that bitcoin ended 8 of the 13 Septembers since 2013 in negative territory. Its average return was minus 2.97 percent and the median was minus 2.44 percent.

So-called "Red September" is a September weakness pattern repeatedly cited in the crypto market. It means the typical September trend itself was weak rather than a few sharp drops dragging down the average. Over the same period, the average return in June was minus 1.59 percent, while October was the strongest with an average of 19.92 percent and a median of 14.71 percent.

Looking at bitcoin's monthly performance, September weakness stands out more. Over the same period, October was tallied as the strongest month with an average of 19.92 percent and a median of 14.71 percent. That is the background for the term "Uptober" in the market.

Last year, however, this conventional wisdom was overturned. Bitcoin ended September 2025 up 5.16 percent, marking a third consecutive September gain, but October that followed ended lower for the first time since 2018.

Wall Street has also experienced similar seasonality. The S&P 500's average September return since 1945 was about minus 0.6 percent, and expanding the range back to 1928 increases the average loss to about minus 1.1 to 1.2 percent. Explanations include selling losers ahead of the mutual fund fiscal year-end, institutions resuming risk-reduction trades after summer vacations, and the U.S. Federal Reserve meeting schedule, but nothing has been announced so far.

Another factor is that bitcoin has recently moved more like high-beta technology stocks. In particular, 2026 is a U.S. midterm election year. In 10 midterm election cycles since 1986, the average low in U.S. stocks was formed on Sept. 2, and the average decline from the prior peak was close to 17 percent. That means seasonal pressure in equities could act on bitcoin at the same time.

Bitcoin began trading in early September around $77,500. After rising about 25 percent in August, its upward momentum has slowed somewhat. An upper resistance zone was suggested at $81,455 to $82,538, and a lower support zone at $73,670 to $75,157.

The macro environment is also increasing market caution. In his first Jackson Hole speech, Federal Reserve Chair Kevin Warsh said the personal consumption expenditures price index recorded an annualised 3.7 percent rate and that the pace of increases was also accelerating on a six-month basis. As a result, the CME FedWatch-implied probability of a September rate hike was reflected at 68.2 percent.

The Fed is set to decide whether to raise rates at its Sept. 15-16 meeting. During that tightening phase, bitcoin fell about 65 percent to a low of $15,500 in November 2022.

Views within the market are also mixed over the September weakness thesis. In early September last year, DYOR CEO Ben Kurland (벤 컬랜드) said the "Red September" formula is closer to a myth than mathematics, but bitcoin plunged during the month and initially repeated the weak pattern. Inflows into spot exchange-traded funds later supported a rebound, and CryptoQuant assessed long-term holders moving into ETFs as a bullish signal. Bitcoin ultimately ended September in positive territory.

Last October, however, led to a bigger shock. After U.S. President Donald Trump threatened on Oct. 10 to impose a 100 percent tariff on imports from China, the crypto market saw $19.0 billion in margin positions liquidated within 24 hours. 1,600,000 traders were forcibly liquidated, and Wintermute said it halted trading entirely, saying the market had broken its internal risk rules. Bitcoin slid in a single day from above $121,000 to below $102,000, and some layer-2 tokens fell 70 percent within hours.

The market is now factoring in September seasonality, interest rate variables and regulatory changes after August's sharp rise. Alongside that, the SEC's proposed "Regulation Crypto Assets," released on Aug. 18, is being cited as a rare pro-regulation factor. Whether bitcoin repeats "Red September" or manages a late-month rebound like last year has become this month's key point to watch through the Fed decision in mid-September.