October is historically the most volatile month for stocks. But why? These 4 popular theories fail to hold up.

October has long carried a reputation as the most turbulent month on the stock-market calendar, a distinction reinforced by infamous crashes in 1929 and 1987. Yet the headline's key point is cautionary: the four popular explanations often offered for October's volatility — ranging from mutual-fund tax-loss selling to the fading of the "summer rally" — don't hold up under scrutiny. If the causes are weak, the pattern itself deserves skepticism.

For investors, the takeaway isn't to prepare for a repeat, but to recognize how easily narrative attaches itself to calendar dates. A month earning a scary label can shape sentiment and headlines without reflecting a durable, measurable effect. Historical averages describe the past; they don't obligate the future to comply.

What to watch: whether volatility actually clusters in October in coming years, and how much of any move is driven by genuine catalysts — earnings, policy decisions, economic data — rather than the calendar itself. Treating seasonal lore as a forecast is a habit worth questioning.