The Atlantic should produce a near-normal 12 storms during the six-month hurricane season that officially begins June 1, while the U.S. coastline has a below-average chance of being struck by a major system, according to Colorado State University’s forecast.

Of the 12 storms, five could become hurricanes and two could grow into major systems of Category 3 or stronger, said Phil Klotzbach, lead author of the closely watched seasonal outlook. The U.S. has a 50 percent chance of being struck by a major hurricane, just below the 20th century average of 52 percent.

“As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them,” Klotzbach wrote in his forecast. “They should prepare the same for every season, regardless how much activity is predicted. ”

In an average year, 12 systems of tropical storm strength or greater form from June 1 through Nov. 30. Already this year, Hurricane Alex formed in January and Tropical Storm Bonnie struck the coast of South Carolina last week.

Klotzbach said his prediction doesn’t include those two, so 2016 could end up with 14 in total. A weakening El Nino in the Pacific Ocean could make conditions in the Atlantic more conducive for tropical storms and hurricanes.

Storms’ Cost

Atlantic hurricanes can exact a high toll in human life, cause billions of dollars in property damage, and roil energy and agriculture markets.

About 5 percent of the U.S.-marketed natural gas production comes from the Gulf of Mexico, along with 17 percent of crude oil, Energy Information Administration data show. The Gulf region also is home to more than 45 percent of petroleum refining capacity and 51 percent of gas processing.

Florida, a frequent target of storms, is the world’s second-largest orange juice producer, behind Brazil. More than 6.6 million homes with an estimated reconstruction cost of $1.5 trillion lie in vulnerable areas along the Atlantic and Gulf coasts, according to the Insurance Information Institute in New York.

El Nino

Among the weather changes wrought by El Nino is a greater chance of wind shear across the Atlantic that can tear storms apart. If the Pacific phenomenon fades, wind shear in the Atlantic will also drop away.

However, water temperatures in the far northern Atlantic, as well as in the subtropical areas of the northeastern part of the basin, are cooler than normal, Klotzbach said. This could indicate a larger shift in what is known as the Atlantic Multidecadal Oscillation (AMO) to a cooler phase.

The Atlantic tends to produce fewer storms when the AMO is in its cooler phase, which can last for 20-40 years. The ocean shifted to its warm phase in 1995, and most of the hurricane seasons since then have produced more than the average of 12 storms a year; 2005 spawned a record 28 storms.

Wilma’s Record

Among those storms was Katrina, which wrecked New Orleans and the central Gulf Coast, and Wilma, the last major hurricane to hit the U.S., with winds of 111 miles per hour or more. The nearly 11 years since Wilma is the longest the country has gone without being struck by a major system.

Last week, the National Oceanic and Atmospheric Administration also predicted the Atlantic would have a near-normal season, for the same reasons cited by Klotzbach. NOAA called for 10-16 named storms, with four to eight becoming hurricanes and one to four becoming major systems. There were 11 named storms last year and eight in 2014.

In April, Klotzbach also called for 12 storms, five hurricanes and two major systems. That forecast was released just days before the death of Klotzbach’s mentor, William Gray, the originator of tropical seasonal outlooks.

“He promised me when I saw him a few days before his death that I would give him at least 50 more years of seasonal forecasts,” Klotzbach wrote in the current outlook. “I will do my best to continue his legacy and produce seasonal Atlantic hurricane forecasts for as long as I can.”