Every few years, the winds shift and the water in the Pacific Ocean gets warmer than usual. The resulting El Nino changes weather worldwide, mostly affecting the United States in winter.
And while the Old Farmer's Almanac is sometimes ridiculed for being unscientific -- for instance, in its prediction of a cold and snowy winter coming up -- the experts on El Nino hedge their bets, too.
One thing already credited, in part, to El Nino -- or maybe it's better said, "blamed on El Nino" -- is last month's record heat. It was the hottest July on record, according to weather agencies around the world.
Here are 11 other things to know about the weather phenomenon known as El Nino.
1 - CURRENT EL NINO IS NICKNAMED 'BRUCE LEE'
Despite the name, this is not a movie, and this El Nino may or may not alleviate drought in California and other areas.
"A big El Nino guarantees nothing," said Mike Halpert, deputy director of the National Oceanic Atmospheric Administration's Climate Prediction Center. "At this point there's no cause for rejoicing that El Nino is here to save the day."
2 - DON’T LIKE 'BRUCE LEE' NICKNAME? HOW ABOUT GODZILLA?
This El Nino is so strong a NOAA blog unofficially named it the "Bruce Lee" of El Ninos after the late movie action hero. The California-based Patzert, who points out that mudslides and other mayhem happens, compares it to Godzilla.
3 - EL NINO PATTERNS TEND TO BENEFIT U.S. ECONOMY OVERALL
While few argue that California needs a wet one, wildfires raging across the state this summer set the stage for flooding and mudslides. Daniel Berlant of the state's Department of Forestry and Fire Protection says crews already have battled 1,500 more fires than a normal year.
But overall, El Nino patterns tend to benefit the United States. Droughts and Atlantic hurricanes are reduced. California mudslides notwithstanding, the U.S. economy benefited by nearly $22 billion from that 1997-98 El Nino, according to a study.
4 - WORLDWIDE BENEFIT… NOT SO MUCH
El Nino does tend to cause problems elsewhere in the world. And while El Nino often puts a big damper on the Atlantic hurricane season, that means more storms in the Pacific, such as Hawaii, Halpert said. So far this year, tropical cyclone activity in the Pacific is far higher than normal.
5 - COULD BE STRONGEST WEATHER CHANGER IN 65 YEARS
The current El Nino, nicknamed Bruce Lee, is already the second strongest on record for this time of year and could be one of the most potent weather changers of the past 65 years, federal meteorologists say.
6 - POSSIBLY HEAVY WINTER RAIN IN SOUTH, EAST
In addition to California, El Nino often brings heavy winter rain to much of the southern and eastern U.S.
7 - POSSIBLY WARMER WINTER IN NORTH AND COOLER IN SOUTHEAST
It's also likely to make the northern winters warmer and southeastern U.S. winters a bit cooler, but not much, Halpert said.
8 - MIDWEST MAY NOT NOTICE
The middle of the U.S. usually doesn't get too much of an El Nino effect, he Halpert said.
9 — 50/50 CHANCE OF MEANINGFUL HEAVY RAIN
California's state climatologist Michael Anderson noted that only half the time when there have been big El Ninos has there been meaningfully heavy rains. The state would need 1-1/2 times its normal rainfall to get out of this extended drought. That's unlikely, Halpert said.
10 - RECORD-SETTERS INCLUDE THREE EL NINOS SINCE EARLY 70s
Still, this El Nino is shaping up to be up there with the record-setters, because of incredible warmth in the key part of the Pacific in the last three months, Halpert said. He said the current El Nino likely will rival ones in 1997-1998, 1982-83 and 1972-73.
11 - BRUCE LEE COULD BE STRONGER THAN KING OF LOS NINOS
NASA oceanographer Bill Patzert said satellite measurements show this El Nino to be currently more powerful than 1997-98, which often is thought of as the king. But that one started weaker and finished stronger, he said.
The Associated Press contributed to this report.