What El Nino could mean for Pa.

With wetter, warmer weather potentially on the horizon for much of the country, here’s what you need to know about El Niño and its potential impacts in Pennsylvania.

What is El Niño?Simply put, El Niño and its counterpart, La Niña, are two opposing climate patterns that represent abnormal conditions in the Pacific Ocean.

Normally, trade winds in the Pacific Ocean blow west along the equator and take warm water from South America toward Asia, according to the National Oceanic and Atmospheric Administration. Through a process called upwelling, cold water rises from the ocean’s depths to replace that warm water.

During El Niño climate patterns, however, those important trade winds weaken, NOAA says. As a result, warm water is pushed back east to the western coasts of North and South America.

El Niño can significantly affect weather across the country, NOAA says. Warmer waters in the Pacific Ocean can alter jet streams and climate systems that help regulate temperatures, rainfall and severe storms throughout the U.S. El Niño also affects marine life in the Pacific Ocean by reducing the availability of cold, nutrient-rich water that underwater ecosystems need to thrive.

The name El Niño, which translates to “little boy” in Spanish, was coined by South American fishermen in the 1600s who first noticed the oceanic pattern. According to NOAA, the full name those fishermen used was “El Niño de Navidad” because the pattern typically peaks in December.

What does El Niño mean for Pennsylvania?Generally, El Niño patterns cause warmer and dryer weather in Canada and much of the northern U.S. More southern states tend to experience wetter weather that can significantly increase flooding, NOAA reports.

Although El Niño’s development is not certain, Pennsylvania is already expected to see warmer weather this spring and summer. The NWS predicts above-average temperatures for much of the Keystone State in late May, June and July, according to the agency’s latest forecast.

As of mid-May, all of Pennsylvania is expected to have at least a 40% chance of observing above-average temperatures throughout late spring and early summer, the NWS’s Climate Prediction Center reports.

Additionally, the southern half of Pennsylvania has an increased probability of observing above-average precipitation in May, June and July. That forecast presents another indicator that may signal the onset of an El Niño pattern, according to the NWS’s seasonal outlook.

Though hurricanes are rarely a direct threat to Pennsylvania, El Niño generally favors stronger hurricane activity in the central and eastern Pacific basins, while suppressing activity in the Atlantic basin, according to NOAA. However, that does not mean hurricanes will not develop in the Atlantic Ocean during the season, which usually stretches from early June through November.

El Niño patterns generally affect winters more than summers in the U.S. According to NOAA, a typical El Niño winter would produce a warmer, dryer winter season for most states in the mid-Atlantic and northeast regions of the country. Southern states, meanwhile, generally see wetter, colder winters under an El Niño pattern.

What about La Niña?La Niña is the counterpart of El Niño. This pattern, which faded as the winter season ended, produces opposite climate effects due to stronger-than-usual trade winds that push more warm ocean water toward Asia.

During La Niña, colder waters in the Pacific push jet streams north, leading to increased droughts in southern states and wetter weather up north. The phenomenon can also lead to a more severe hurricane season.