Stocks: 4 things to know before the open

S&P futures 2014 09 30
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It looks like the month of September could end with a whimper.

Here are four things you need to know before the opening bell rings in New York:

1. Goodbye September: The past month has been difficult for investors.

Ahead of the final trading day of the month, all the main U.S. indexes were in the red. The Nasdaq has been hurting the worst, down by about 1.6% over September. The S&P 500 also dropped by just over 1%.

Meanwhile, the declines on the Dow Jones industrial average have been mild. With U.S. stock futures shifting higher Tuesday, it's possible the Dow could eke out a gain for the month. But don't hold your breath.

2. Hong Kong drop: Hong Kong's main stock market index, the Hang Seng, kept falling Tuesday as large pro-democracy protests show no signs of abating. The index has dropped for the past four trading days.

Given considerable uncertainty over how the protests will play out, investors are selling Hong Kong stocks or sitting on the sidelines.

Anemic Chinese manufacturing data for September also dampened sentiment. The widely watched HSBC index tracking the sector was revised down slightly for the month, to 50.2 from the initial reading of 50.5.

Related: Fear & Greed Index

3. Economics and earnings: Be ready for the S&P/Case-Shiller home price index to come out at 9 a.m. ET. And the Conference Board will publish its monthly consumer confidence index at 10 a.m. ET. Walgreens (WAG) is the main company reporting earnings before the opening bell.

Related: CNNMoney's Tech30

4. European overview: European markets were broadly higher in early trading, with the exception of the FTSE 100. The CAC 40 in Paris was advancing by 0.4%, other major indexes posted narrower gains.

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