An atmospheric river pounding the Pacific Northwest has ushered in cold temperatures across Northern California, prompting meteorologists to advise pet owners to provide proper care for their pets during the cold weather.

The atmospheric river – a narrow corridor of concentrated moisture coming from the Pacific Ocean – is one of the strongest storms of its kind to hit Northern California so far this season, with meteorologists predicting heavy rain and mountain snow this week. Bad weather conditions are also expected in Oregon and Washington when the storm hits.

In the early morning hours Monday, National Weather Service (NWS) meteorologists at the Sacramento office issued a freeze warning advising of low temperatures.

“Low temperatures of 30 to 36 degrees and frost possible tomorrow morning at altitudes below 600 metres,” the warning said. “These cold temperatures can be dangerous to pets, plants and people without adequate heating. Frost and freezing conditions can affect sensitive vegetation.”

The freeze warning is in effect for the Carquinez Strait and Delta, Sacramento Valley, the Mother Lode region, the mountains from southwestern Shasta County to western Colusa County, the northeastern foothills, the northern San Joaquin Valley, Shasta Lake and northern Shasta County. The warning is expected to last until 10 a.m. local time on Tuesday.

“Take steps now to protect those vulnerable to the effects of cold weather,” the warning read.

NWS Chief Meteorologist Nathan Rick explained Newsweek that the temperature is about 10 degrees below normal for this time of year. Average low temperatures are in the lower 40s.

It’s the first time temperatures have dropped in the fall/winter season, Rick said, prompting the freeze warning.

“We expect a pretty sustained period of precipitation from Tuesday afternoon into the weekend,” Rick said, adding that temperatures will remain low all week, about 5 degrees below normal.

The freeze alert is just one of several weather warnings issued in the region as the atmospheric river arrived.

Atmospheric rivers are a “long, narrow region of the atmosphere, like rivers in the sky, that transport most of the water vapor outside the tropics,” according to the National Oceanic and Atmospheric Administration.

Other weather warnings issued across California include a winter storm warning, a high wind warning, a flood warning and numerous others.

While atmospheric rivers can help alleviate drought, winter storms also cause devastating floods and landslides. Meteorologists are predicting another wet winter for the West Coast, according to an AccuWeather report released earlier this season, with atmospheric rivers expected to focus on Northern California earlier in the winter season before shifting to Southern California in January.