5 Fort Hood soldiers dead, 4 missing amid Texas flooding

This is the second year in a row that Texas has been hit by 500-year floods, which has caused meteorologists and other experts to point toward climate change or the weather pattern El Niño as potential culprits.

"It could just be really bad luck," said CNN Senior Meteorologist Brandon Miller. "A 500-year flood doesn't mean you will go 500 years between them. It just means it is such an extreme event that the odds of it happening are very low, therefore it only happens on average every 500 years.

"It just so happens that parts of Texas have seen them now in back-to-back years, and maybe even twice this year. The odds of that happening are infinitesimally small."

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"Basically, it's a 1-in-500 chance of it happening in any year," said CNN Meteorologist Taylor Ward. "Happening twice in a single year is very bad luck."

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NASA early in the year warned that EL Niño weather event -- characterized by warming waters in the eastern Pacific Ocean -- was already one of the three strongest ever recorded.

Climate change is another possible culprit because one of the expected impacts from a warmer climate is heavier rainfall, prompting more flooding, such as the ones in South Carolina last year, Miller said