Euro just hit its weakest point vs the dollar since May. That's a pretty sharp move in a short window.

When the euro weakens like this, it usually signals one of two things: either the Fed's keeping rates higher for longer than Europe, or growth expectations are diverging fast. Right now it's probably both.

For U.S. investors, this matters because a stronger dollar can weigh on multinationals with heavy European exposure. Think about companies that generate significant revenue overseas—currency headwinds eat into earnings when they convert euros back to dollars.

Also worth watching: if the euro keeps sliding, European stocks might look cheaper to U.S. buyers, but you're also taking on FX risk. The currency exchange rate can give or take away your gains.

Bottom line: dollar strength is real, and it's showing up in the euro exchange rate. Keep an eye on how this plays out for earnings season.