September’s Secret Weapon? The Dollar Index

September is famous for the shadow of global markets – from stocks and bonds to gold, and history shows that few assets escape from the seasonal recession that usually affects this month. But there is an external one that is delivered again and again when everything stumbles: the US dollar.

With the start of September, investors make the risks from the table and turn into cash.

while SPDR S & P 500 ETF TRUST (NYSE: SPY) has reached a average decrease of 1 % in September during the past decades, gold has recorded a decrease of 1.81 % over the past ten years in the same month, and the US dollar index (DXY) has shown calmly, reliable.

In the past ten years, the DXY index has gained 0.91 % on average in September, with the upper month of 7 out of 10 times – the best performance of any month in this period.

Returning to 20 years, the trend stands. The dollar achieved a positive average in September by 0.50 %, with a 60 % victory rate, making it the third best month for the US dollar index after May (an increase of 0.84 %) and October (an increase of 0.52 %).

This pattern indicates a seasonal rotation to criticism, often driven by increased fluctuations, risk alienation, and reducing liquidity across the markets.

So far, in 2025, it was narrated completely different from the dollar.

The US dollar index decreased by 9.6 % on an annual basis until September 3, and hit the uncertainty related to tariffs and expectations about the easiest federal reserve policy.

In August alone, DXY 2.2 % slipped. But here is the place where history becomes interesting:

In the past twenty years, when the dollar had a public negative performance to the date of the end of August, September was closed with gains in four cases, with an average return of 0.52 %.

The most interesting is the short -term reflux that often follows August for Greenback.

When the dollar fell in August, four September ended in green, with a average profit by 0.18 % in general.