PORTLAND, Ore. ( KOIN ) – El Niño, the climate pattern that brings drier and warmer than usual weather to the Northern U.S. and Canada and wetter than usual conditions to the Gulf Coast and Southeast, has officially arrived, scientists announced Thursday.

The National Oceanic and Atmospheric Administration’s Climate Prediction Center released a monthly outlook Thursday in which forecasters issued an El Niño advisory . El Niño conditions are present and are expected to gradually strengthen into the winter, forecasters said.

The climate phenomenon is marked by warmer-than-average sea surface temperatures in the central and eastern Pacific Ocean near the equator. El Niño occurs on average every two to seven years.

The last three years have been La Niña , which has the opposite effect of El Niño. La Niña tends to bring drought to the Southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada. Winter temperatures also tend to be cooler than normal in the North.

KOIN 6 News Meteorologist Kelley Bayern said she hopes the arrival of El Niño means the upcoming winter in the Pacific Northwest will be calmer.

The last El Niño winter was 2018-2019 and Portland received 7 inches of snow that year, which is above normal.

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“On average, El Niño winters produce below-normal snowfall in PDX with an average of 2.4″ in the city,” Bayern said.

The average Portland winter snowfall is 4.2 inches.

There have been 13 El Niños since 1980.

In general, Portland has seen a drastic change in its snowfall over the decades. Seasonal averages in the 1950s were closer to 8 to 9 inches of snow per year versus the 4 to 5 inches of snow over the last 40 to 50 years.

El Niño’s impact will be felt more in the late fall through spring than during the summer.

“By winter, there is an 84% chance of greater than a moderate strength El Niño, and a 56% chance of a strong El Niño developing,” NOAA said.

Climate experts warn that climate change can exacerbate or mitigate certain impacts related to El Niño.

“For example, El Niño could lead to new records for temperatures, particularly in areas that already experience above-average temperatures during El Nino,” Michelle L’Heureux, a climate scientist at the Climate Prediction Center said.

Scientists have been expecting El Niño’s development for the last few months and issued the first El Niño watch on April 13.

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