Keep boots and other rain gear handy – you may need them often in you're in the South or California. A severe weather pattern known as El Nino could be the most powerful on record, federal weather-watchers say. It already is the second-strongest for this season in more than 60 years of record-keeping, says the National Oceanic and Atmospheric Administration (NOAA), a federal climate agency. This is "very likely to be the warmest year on record," predicts a Stanford University specialist.

El Nino starts with above-normal water temperatures in the Eastern Pacific and can affect weather around the world. For the United States, it can bring heavy winter precipitation in California and across the South. At the same time, areas around the northern Rocky Mountains and Great Lakes probably will see less than the usual levels of rain and snow.

The pattern is "continuing to strengthen as expected," posts respected California weather blogger Daniel Swain, a Stanford University doctoral student in earth system science. "All available evidence continues to point toward continued strengthening into the fall months and persistence through winter 2015-16." But even if El Nino brings lots of rain to the California, "one season of additional rain and snowfall is unlikely to erase four years of drought," says Mike Halpert, deputy director of NOAA's Climate Prediction Center.

Origin of the name: In Spanish, El Nino refers to the Christ child (Jesus), and the weather system got its name because periodic warming in the Pacific near South America is often noticed around Christmas.

Federal forecast says: "There is a greater than 90% chance that El Nino will continue through Northern Hemisphere winter 2015-16, and around an 85% chance it will last into early spring 2016." -- NOAA, Aug. 13 statement

NASA specialist says: "This definitely has the potential of being the Godzilla El Nino." -- Bill Patzert, climatologist at the space agency