September Brings 3 Warning Signs for Bitcoin Following 24% August Rally

Bitcoin (BTC) posted a gain of about 24% in August, marking its biggest monthly rise in 2026. The August rally pushed the cryptocurrency from the $60,000 range to a brief peak above $80,000.

Yet three cautionary signals have appeared: exchange reserves, ETF flows, and spot demand all became less favorable in the final days of August.

Binance Reserves Reach 2026 High, Adding to Bitcoin Warning Signs

CryptoQuant data shows Binance’s bitcoin holdings rose to about 687,000 BTC, a 2026 high. After falling to around 617,000 BTC in late April, reserves reversed course. The build then picked up speed during August as bitcoin gained.

Typically, traders transfer coins to exchanges for selling, hedging, or posting as collateral. Consequently, an increasing reserve during a rally means more supply is instantly ready for sale.

The figure by itself is not conclusive. Wallet restructuring, custody changes, and market-making moves can also boost exchange reserves.

Yet those coins now reside on the biggest platform, while falling stablecoin reserves on exchanges provide less cash to absorb them.

“A yearly high in Binance reserves near major resistance is a warning sign. The next move above $80,000 will likely depend on whether spot and ETF demand can absorb the additional supply potentially available to the market,” XWIN Japan wrote.

Weekly ETF Demand Halves as Nine-Day Inflow Streak Ends

On August 28, US spot bitcoin ETFs saw a net outflow of $201.8 million, per SoSoValue. That negative day broke a streak of nine straight inflow sessions, which occurred as Bitcoin notched its largest-ever weekly dollar gain.

Other major ETF products remained positive that day. Ethereum (ETH) funds attracted $102.18 million, and XRP (XRP) and Solana (SOL) products recorded $26.2 million and $18.08 million in inflows, respectively.

Weekly flows also slowed. In the week through August 28, net inflows dropped 51.8% to $924.5 million, compared to $1.92 billion the prior week.

A single negative day does not signal a trend shift. Yet ETF flows represent a key demand driver for Bitcoin, and that source may be weakening.

Leverage, Not Spot Demand, Could Be Powering the Rally

Lastly, analyst Crypto Rover contended that the weekend rally had little spot buying behind it.

“BTC is moving higher over the weekend while spot CVD remains almost flat, suggesting leverage is driving the move. Last time we spotted this same setup, Bitcoin dumped from $81K to $77K,” the post read.

Spot cumulative volume delta (CVD) measures the difference between aggressive buying and selling in spot markets. When CVD stays flat while prices rise, it may indicate that leveraged positions or derivatives, not solid spot demand, are pushing the move.

The situation is not unanimously interpreted that way. GSR’s Andy Baehr described the $80,000 breakout as a new market regime driven by ETF demand and short covering.

Historical patterns provide little reassurance. According to Coinglass, September has seen an average decline of 3.08% for Bitcoin since 2013, making it the worst-performing month on average.

Recent Septembers have gone against the trend. The past three Septembers all ended in positive territory, with increases of 5.16% in 2025 and 7.29% in 2024.

In the days ahead, it will become clear if spot and ETF buyers can absorb the coins sitting on Binance.