SOURCE: Washington Post

DATE: June 8, 2018

SNIP: Almost every tract of land in the contiguous United States was warmer than normal in May, helping to break a Dust Bowl-era record.

The month’s average temperature 0f 65.4 degrees swept by the previous high mark of 64.7 degrees set in 1934. Temperatures were more than 5 degrees above normal, according to the National Oceanic and Atmospheric Administration, which published a May U.S. climate assessment Wednesday.

The 1934 record was impressive, enduring for decades even as the climate has warmed because of increasing greenhouse gases in the atmosphere. One of the main reasons May 1934 was so hot was because it was so dry, posting the least precipitation for the month on record. When the land surface is dry, it heats up faster.

In May 2018, temperatures soared to record levels even without as much help from dry soils. Precipitation was a hair above normal averaged over the nation. Maryland, hit by major floods in Frederick and Ellicott City, had its wettest May on record. So did Florida. Asheville, N.C., posted 14.68 inches of rain, its wettest month in history.

Rather than dry soil, the record warmth this past May can be traced to the jet stream, the high-altitude current that separates cold air from warm air. It lifted north of the U.S.-Canadian border for much of the month, allowing widespread abnormally warm air to flood northward.

It’s also fair to say that rising greenhouse gas concentrations, which have pushed May temperatures higher over time and now even above those torrid Dust Bowl years, contributed to the record temperatures.

Across the nation, more than 8,500 warm-temperature records were set at weather stations during the month, compared with 460 cold records.