A massive marine heat wave spanning much of the Pacific Ocean is raising concerns among climate scientists, who say the unusually warm waters could fuel extreme weather worldwide in the coming months, including stronger tropical cyclones, dangerous heat in the western United States, and an increased risk of flooding along the California coast, The Washington Post reported over the weekend.

The marine heat wave currently covers an area stretching from the Philippines to Peru and north to Hawaii and the California coast, encompassing roughly 13.5% of the Earth's surface — an expanse more than eight times the size of the contiguous United States.

Scientists say the event developed after two separate marine heat waves merged: one in the North Pacific and another associated with a strengthening El Nino along the equator.

Marine heat waves are prolonged periods of abnormally warm ocean temperatures and are classified on a five-category scale based on their intensity and duration, ranging from moderate to beyond extreme.

Researchers say the vast reservoir of warm water is already influencing global weather patterns.

Climate scientist Dillon Amaya said months of elevated ocean temperatures could have significant consequences throughout the coming winter and into next spring.

Among the most immediate concerns is Super Typhoon Bavi, which is expected to draw energy from exceptionally warm waters in the western Pacific as it moves near the Northern Mariana Islands before potentially affecting Taiwan and eastern China later this week.

Forecasters also say atmospheric changes associated with the marine heat wave could contribute to the development of a powerful heat dome over the western United States in mid-July, bringing dangerously high temperatures and increasing wildfire risk.

War Department meteorologist Eric Webb said the developing weather pattern could significantly increase heat and wildfire threats across parts of the Southwest and the southern Rocky Mountains, particularly north of New Mexico and Arizona, where large wildfires have already burned this season.

Scientists are also warning of longer-term impacts along the U.S. West Coast.

Climate scientist Daniel Swain said unusually warm Pacific waters could raise sea levels along California by between 6 inches and 2 feet in the coming months. Combined with winter storms and king tides, those elevated sea levels could produce coastal flooding that exceeds historical records.

Swain urged state and local governments to begin preparing for an increased likelihood of damaging coastal flooding and unusually powerful winter storms, while emphasizing that such outcomes remain more likely than certain.

The effects may extend well beyond the Pacific coast.

Scientists say the accumulated ocean heat is expected to strengthen the subtropical jet stream during the fall and winter, potentially creating a more active storm track across portions of the southern and eastern United States. That pattern could increase the likelihood of heavy rainfall, flooding and severe thunderstorms.

Climate scientist Kevin Trenberth said warmer ocean temperatures increase evaporation, allowing the atmosphere to hold more water vapor that can later fuel heavy rainfall thousands of miles from where the moisture originated.

Marine heat waves have also developed in other parts of the world. Following a deadly June heat wave in Europe, unusually warm waters have spread across portions of the Mediterranean Sea, where scientists say they could reinforce additional episodes of extreme heat into mid-July.

Researchers say marine heat waves develop through a combination of weakened winds, reduced ocean mixing, changes in atmospheric circulation, and shifting ocean currents. The current Pacific event is linked in part to the Pacific Meridional Mode, a natural climate pattern characterized by weaker winds and reduced evaporation, which scientists say has combined with the developing El Nino to create exceptionally widespread ocean warming.