First significant snowfall of the season is set to hit Washington, Oregon and Montana – as temperatures in NYC are set to hit 81 degrees! See how El Nino will affect your region

The first significant snowfall of the winter will hit parts of the US Northwest and Northern Plains later this week, while other parts of the country can expect summer-like temperatures thanks to El Nino.

Snow is expected as early as Monday evening or Tuesday morning, with a wave of cold air and deep moisture spreading from Washington and Oregon through much of Montana.

A storm is expected in the northwest Tuesday night.

Higher altitudes have been warned to expect possible heavy snow, disrupting travel.

Several major high-altitude mountain passes in the Cascades, including Stevens Pass, Snoqualmie Pass and Stampede Pass, could be affected.

Snow is expected as early as Monday evening or Tuesday morning, with a wave of cold air and deep moisture spreading from Washington and Oregon through much of Montana.

The rest of the northwestern US will get its first snowflakes on Tuesday afternoon into the evening.

Idaho, Montana and the Cascades in Oregon will also begin accumulating snowfall, with temperatures hovering around freezing.

On Tuesday night, temperatures in high-altitude areas will drop well below freezing.

Temperatures in northern Idaho will drop into the teens early Wednesday morning, while parts of northwestern Montana will drop into the single digits.

Heavy snow will fall Tuesday night due to the combination of cold air and moisture.

Tuesday evening, six inches or more of snow could pile up quickly at pass levels in the Cascades, with amounts approaching a foot possible for areas above 7,000 feet.

Snow will continue to fall in the Northwest and Northern Rockies on Wednesday.

During this time, wind speeds will also increase and snow will start blowing, which could significantly reduce visibility and impair travel.

Temperatures will generally be warmer than average in the northern U.S., the National Oceanic and Atmospheric Administration predicts

The organization also estimates that the south will have a wetter than average winter through February

Higher altitudes have been warned to expect possible heavy snow, disrupting travel

On Wednesday, parts of Washington will accumulate several inches of snow up to 1,000 feet, but Seattle will see only cold rain.

Snow will begin falling across the Cascades on Thursday, but will then spread to parts of the Northern Plains as the storm moves east.

More than a foot of heavy snow will blanket parts of South Dakota Thursday and into Thursday night.

Significant snow accumulation will end across much of the northern U.S. on Friday, but some flakes will still fly along the U.S.-Canada border before the storm fully spreads across southern Canada .

Still, the northern U.S. will experience warmer-than-average temperatures overall, the National Oceanic and Atmospheric Administration predicts.

The warmer weather will be felt in Alaska, the Pacific Northwest, northern New England – and in New York City, where temperatures are expected to reach 81 degrees.

The upper Midwest, California and parts of the South will also likely be warmer than average.

The organization also estimates that the south will have a wetter than average winter through February.

Above-average precipitation levels are likely to affect Florida, southern Georgia and southern Alabama

The warmer, wetter weather is caused by the effect known as El Niño.

El Niño occurs every two to seven years when ocean temperatures in the central and eastern Pacific Oceans warm, affecting weather patterns around the world, according to the National Weather Service.

This winter’s El Niño – the first in four years – has a 30 percent chance of being as strong or stronger than strong El Niños of the past, including those of the winter of 1997-1998 and the winter of 2015 -2016, according to NOAA.