A 2018 Summer of Extremes

Meteorological summer has been one of extremes in the U.S. Overall, the East has been wet while the West has baked in the heat. These types of extremes, which are set up by a consistent jet stream pattern, are amplified by a warming climate.

Many locations in the Middle Atlantic, Ohio Valley, and Upper Midwest had one of their 10 wettest summers on record, with Maryland and Pennsylvania at the heart of the summer deluge. Baltimore was among the cities in their top 10, getting more than 24 inches of rain. Massive flooding hit central and eastern Pennsylvania in July. More than 15 inches of rain fell in the town of Lebanon in July, and 12-15 inches were common monthly totals around the state capital of Harrisburg. The supercharged water cycle that comes with a warming climate is reflected in the increase in heavy precipitation. The heaviest rainfall events are getting heavier, with a 55 percent increase in the amount of precipitation falling in the heaviest events in the Northeast.

Even in the unrelenting summer heat in the Southwest, occasional summer monsoon thunderstorms can provide some relief from the heat. Enough of them came together to give Prescott, Arizona one of its 10 wettest summers on record.

Nearly all states across the U.S. have sites with one of their 10 hottest summers on record, but the core of the heat has been in the Southwest, and that continues to play a role in the devastating wildfire season in California. The Mendocino Complex fire north of San Francisco is the largest on record in the Golden State.