This May was the United States’ wettest month in all 121 years of record-keeping, according to the National Oceanic and Atmospheric Administration (NOAA).
A total of 4.36 inches fell across the lower 48 states last month — 1.45 inches more than average, NOAA said Monday. Fifteen states saw precipitation that was “much above average” in May, and Oklahoma and Texas experienced their wettest month on record, with precipitation levels “more than twice the long-term average,” according to NOAA.
These records aren’t surprising for Oklahoma and Texas, which have been battling severe storms and major flooding over the last several weeks. These floods have swept away homes and have killed at least 28 people in the states. Scientists don’t yet know how much climate change played into these floods, but they noted to ThinkProgress last month that climate change is expected to make severe flooding like this more common.
“There are several factors that have created conditions that made it more likely to have this disastrous situation, and I would say the majority of them are natural factors,” Brenda Ekwurzel, a senior climate scientist with the Union of Concerned Scientists, told ThinkProgress. “However, there’s a definite climate assist that creates the likelihoods of the odds of it being a more severe event.”
Along with this increased chance of heavy rainfall, scientists also say that some regions will see longer, more intense periods of drought — periods that then could be followed by heavy, intense rainfall. Warmer air can hold more moisture, which means that moisture can collect in the atmosphere for longer than usual and then fall all at once on a region. This “weather whiplash” exacerbates the risk of flooding, as the heavy rain can simply run off the surface of the dry, hard earth, rather than being absorbed by it.
While the U.S. as a whole got more precipitation in May than it has in over a century, not all states saw wet weather. Nearly 70 percent of California is still in an extreme drought, and 99 percent is still abnormally dry. The drought, which scientists have said has “very likely” been exacerbated by climate change, has led to the state’s first-ever water rationing program and could end up costing the state’s economy $2.7 billion in agricultural losses.
However, in spite of California’s extreme drought, NOAA noted Monday that 24.6 percent of the contiguous U.S. is in drought as of the June 2 drought monitor — the smallest “drought footprint” in the country since February 2011.
“Drought conditions drastically improved across the Southern Plains. Drought improvement was also observed across the Central and Northern Plains, Upper Midwest, and the Central Rockies,” NOAA stated. However, it added, “drought conditions remained entrenched in the West” in May.
NOAA also noted another record in its report Monday: Alaska had the hottest May statewide average temperature last month in 91 years of record-keeping. The temperature — 44.9°F — was 7.1°F above average. “The warmth in Alaska was widespread with several cities were record warm, including Barrow and Juneau,” NOAA noted.