The S&P 500 seasonal window opened on Wednesday. Since 1950, the index has risen from mid-October to year-end in 80% of years.

However, hotter US inflation is testing that record on day one. The index fell 0.75% after recently hitting record highs.

Why Mid-October Marks the Turn for Stocks

Charles Edwards, Capriole Investments founder and BeInCrypto Market Intelligence Expert Council member, flagged the date Wednesday.

“Today is the start of the best 60 days of the year for stocks.”

BeInCrypto’s own calculation from daily closes backs the claim. From the Oct. 13 close to year-end, the S&P 500 gained in 61 of 76 years.

The median gain in that stretch was 4.2%. In contrast, an average period of equal length returned about 2% and rose only 66% of the time.

Kyle Doops, Crypto Banter host and fellow Council member, compared 2026 with the 30-year average. That average dips into mid-October, then climbs through December.

The S&P500 usually shows increased strength into end of year when comparing with the last 30 years. pic.twitter.com/Q3BXnHxPpI

— Kyledoops (@kyledoops) October 14, 2026

Can a Strong 2026 Keep the Year-End Pattern Alive?

History favors strong years. When the index entered the window up 10% to 20%, it finished higher in 21 of 25 cases.

Gains also cluster in one month. November rose in 13 of the last 14 years, while December averaged only 0.10%, according to Forecaster.biz data.

Meanwhile, the risks are concrete. September inflation data showed prices up 3.7% year-on-year, above forecasts, as gasoline jumped 9.1% in a month, the BLS reported.

The Federal Reserve hiked in September, and a second move before year-end is now in play. In 2018, a midterm year with Fed hikes, the window lost 9.4%.

Still, a four-year bull market and expected third-quarter earnings growth of 29.2%, per FactSet, give seasonality a fundamental base. Whether earnings can outrun 5% Treasury yields will likely decide which side of the 80% this year lands on.