Get ready for an "extremely active" active Atlantic hurricane season, government forecasters said today.

Between now and the end of the Atlantic hurricane season (Nov. 30) the National Atmospheric and Oceanic Administration predicts 13 to 20 named storms, of which seven to 11 could become hurricanes. Three to six of those hurricanes could be major, with winds 111 mph or greater.

As alarming as these numbers might be, NOAA officials stress they cannot predict the number of hurricanes that will actually strike U.S. soil. The last major hurricane to make landfall in the U.S., Wilma, struck in 2005. Since then, a total of five Category 1 or 2 storms (with winds up to 100 mph) have hit the U.S.

Three climate factors are coming together to produce an "active" or "extremely active" hurricane season, NOAA forecasters said today. Ongoing climate patterns off the coast of Africa have spawned a period of high hurricane activity since 1995. Water temperatures are warmer than average in the Atlantic and the Caribbean. El Niño conditions in the Pacific Ocean are absent this season; those tend to keep hurricanes from forming.

The 2013 prediction follows an especially active 2012 Atlantic season, which produced 19 named storms. (The average is 12, according to NOAA.) Of those storms, 10 became hurricanes and two became "major" hurricanes packing wind speeds 111 miles an hour or greater. Two tropical storms fired up in May, even before the official start of the 2012 season: Alberto and Beryl. The deadliest 2012 storm by far was Sandy, which killed at least 147 people as it raked its way across the Caribbean to the Eastern Seaboard.

In the U.S., Sandy caused approximately $50 billion in damage.

On Monday, NOAA predicted a below-normal hurricane season for the Central Pacific Basin.

"Now is the time to start thinking about the hurricane season that is coming," said NOAA acting director Kathryn Sullivan. "Make your plans."

National Hurricane Preparedness Week is May 26 through June 1.