The 2020 Atlantic hurricane season is off to a record start with nine storms forming across the basin faster than any year going back to at least 1851. Tropical Storm Isaias, the most recent, is tracking along the U.S. East Coast and could make landfall in the Carolinas overnight.

Notes: Forecast is in Eastern Time. Includes unnamed tropical systems.

In a typical year, the Atlantic doesn’t experience nine named storms until early October, according to the U.S. National Hurricane Center. While overall the storms in 2020 have been relatively weak—only two have reached hurricane strength—the tally is only three shy of the 12 usually seen through an average six-month season.The most active hurricane season on record was in 2005, which also began relatively early and produced 28 storms—including Katrina. While El Niño may have contributed to the high number of storms in 2005, heightened activity this year can’t be blamed on any extraordinary climate phenomenon. As greenhouse gas emissions warm the earth, oceans are absorbing much of the excess heat, increasing the likelihood of more extreme weather events.

Analysis from Phil Klotzbach, a meteorologist at Colorado State University, shows that sea surface temperature anomalies in the tropical Atlantic are at their fourth highest levels on record. The three years that were warmer—2005, 2010 and 2017—all had extremely active hurricane seasons.

Average sea surface temperature, July 2020

NOAA’s Climate Prediction Center expects 13 to 19 named storms and up to 10 hurricanes—of which up to 6 could become major hurricanes with winds of 111 mph or higher. A report by Colorado State University estimates a total of 20 named storms, 9 hurricanes and 4 major hurricanes this season.