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Hurricane Harvey strengthens, and these stocks could get hit

Key Points
  • Harvey threatened the Texas coastline as it strengthened into a Category 3 hurricane, which would be the worst to hit the U.S. mainland in more than a decade.
  • A CNBC analysis of markets around Category 2 and Category 3 storms since the 1980s using Kensho found that energy stocks tended to climb and utilities stocks tended to fall in the month after landfall.
  • But insurance stocks' performance varied depending on hurricane strength.
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Hurricane Harvey strengthened to a Category 3 hurricane Friday afternoon, threatening the U.S. Gulf Coast as the type of storm that has historically tended to send utilities and insurance stocks lower.

Harvey is quickly turning into the worst hurricane to hit the U.S. mainland in more than a decade, and is expected to cross over the Texas coast by early Saturday. The National Hurricane Center expects Harvey to linger over the state for days. Houston and the Texas coastline could experience heavy flooding, authorities in the energy-producing state warned.

"Until now hurricanes have not directly threatened the infrastructure and production associated with the US shale-inspired export boom," Michael Cohen, head of energy markets research at Barclays, said in a Friday report. "We think that the flooding impact of Hurricane Harvey could make it more destructive to US crude and product supplies as well as port facilities than the market is currently assuming."

A man carries a sheet of plywood as he helps board up windows in preparation for Hurricane Harvey, Thursday, Aug. 24, 2017, in Corpus Christi, Texas.
Eric Gay | AP

Using quantitative analytics tool Kensho, CNBC looked at Atlantic hurricane and tropical storm landfalls since the 1980s and found that utilities stocks tended to fall, while insurance stocks' performance depended on hurricane strength.

With a Category 2 storm or less at landfall, insurance stocks climbed an average 0.5 percent in the month following, according to a Kensho, as the companies likely didn't need to spend as much on claims as in stronger storms.

Insurance stocks in the S&P 500 subsector include AIG, Travelers Cos., Loews, Prudential Financial and Allstate.

The Kensho study looked at 58 occurrences of a Category 2 hurricane or less at landfall since September 1984.

Energy stocks were among the best performers, rising an average of 1 percent in the month following. Utilities were among the worst performers, falling an average half percent in the month after the hurricane's landfall, the analysis found. The S&P 500 historically saw no change.

With a Category 3 storm and severe flooding, however, insurance and utilities stocks tended to fall more than 1 percent over the month following, according to Kensho. The study looked at 24 instances of Category 3 or greater hurricanes at landfall since August 1983.

Energy stocks gained an average 0.4 percent over the next month, while the S&P 500 climbed an average 0.9 percent, the analysis showed.

"Hurricane Harvey is likely to fuel bullish market sentiment [for energy products] through the first half of September," Barclays' Cohen said. "If crude and refined product impacts are severe, this will impact EIA's weekly data releases for at least this coming month, thereby adding to bullish market sentiment."

The Saffir-Simpson Hurricane Wind Scale ranks storms from Category 1 to 5, with 5 being the strongest.

— CNBC's John Melloy and David Gernon contributed to this report.

Disclosure: CNBC's parent NBCUniversal is a minority investor in Kensho.

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