It's no surprise that many sectors typically drop in the fall, given that September is notoriously a rough month for the entire market. But that means investors who shop carefully can find some rewarding bargains.

On average, the S&P 500 technology, industrials, materials, healthcare, and consumer-staples sectors all drop more than 1% from various dates in September through dates in October, according to SentimenTrader. The firm crunched data from S&P 500 sector exchange-traded funds, all of which launched in the late 1990s.

These moves can present attractive buying opportunities. "Treat a pullback during an unfavorable seasonal window as a longer-term buying opportunity," write analysts at SentimenTrader.

It's possible that all five sector ETFs that SentimenTrader spotlighted have a bright future, but we like a couple in particular.

The State Street Materials Select Sector SPDR ETF is a candidate to put on your buy list. It averages a nearly 3% drop from its September peak to its October trough, before rising just over 7% through the end of the year. That's more volatile than the S&P 500's 1.3% average September drop since 2000 and its average rise of 6.8% from the bottom through year-end, according to Dow Jones market data.

These numbers, at least on the surface, make sense because materials stocks are largely "cyclical," or sensitive to shifting economic winds, meaning they can see an outsize boost to profits during periods when the economy is growing. The materials sector includes metal miners and manufacturers, chemical makers, and other basic materials producers. Customers from across different sectors buy more from these companies when their demand looks stronger and buy less when demand starts to weaken, making materials companies' earnings and stock prices fairly volatile.

Buying the sector on a September dip-which hasn't happened yet-makes sense, as the market continues to expect earnings growth. The economy continues to grow, and even if the Federal Reserve hikes interest rates once in the face of inflation this year, there's a chance it could then cut next year, which would help the economy and the materials sector. Analysts currently expect companies in the materials fund to achieve 11% aggregate earnings in 2027, according to FactSet, and given the current economic environment, that's certainly within reach.

That can boost the stocks, which aren't particularly expensive. The ETF trades at just over 17 times earnings per share for the coming twelve months, about 12% below the S&P 500's just over 19 times. That's right around the middle of the range of the fund's earnings multiple relative to the S&P 500 in the past five years, indicating that, if earnings meet or beat estimates, the ETF has room to rise-particularly once it has already taken a beating this fall.

Elsewhere, don't shy away from buying tech on a dip. Historically, the State Street Technology Select Sector SPDR ETF drops just over 1% from its September peak to the bottom, and it then rises more than 6% from there though the end of the year. That's enough to make a buyer who is waiting in the wings comfortable, given the growth the tech sector is currently experiencing.

True, one of the pressing issues right now is the high uncertainty about when spending growth on data centers will slow down. Oracle, Meta Platforms, and Alphabet have borrowed tens of billions of dollars to help finance their data-center and chip spending, so if they slow investments, the chip makers could see disappointing profits.

But that risk-potentially a distant one-will become priced in to tech, and chip stocks specifically, making them look attractive.

Don't take it from us. Dell Technologies is seeing explosive data-center server demand, and just beat estimates for earnings and guidance. That came not long after Nvidia issued a far stronger-than-expected outlook for 2028 demand. Cyber security software leader Palo Alto Networks crushed profit estimates.

AI and the broader tech industry remain in growth mode. Analysts see 36% aggregate EPS growth next year.

So, wait for pullbacks in these sectors, but don't wait too long.