WASHINGTON (AP) — The La Nina phenomenon that may have helped boost last year’s hurricane season and this spring’s tornadoes has ended.

The Climate Prediction Center said Thursday that the periodic cooling of the tropical Pacific Ocean known as La Nina ended in May and the ocean returned to neutral conditions. La Nina and its warm-water opposite El Nino can affect weather worldwide.

The end of this La Nina could be good news. La Nina years sometimes have more hurricanes and tornadoes than average, and some researchers say the phenomenon may have contributed to the twister outbreak in May. In addition, last summer there were 19 named tropical storms and hurricanes in the Atlantic and Caribbean, though only one, Hermine in September, did much damage in the United States.