Above-average precipitation across the country made last month the wettest December on record, helping ease drought conditions for many states, according to a newly released National Oceanic & Atmospheric Administration (NOAA) report. Additionally, NOAA also reported that 2015 was the second-warmest year on record (Figure).
The 2015 annual average U.S. temperature was 54.4°F, which is 2.4°F above the 20th-century average. Only 2012 was warmer for the U.S., with an average temperature of 55.3°F, NOAA said.
“This is the 19th consecutive year the annual average temperature exceeded the 20th-century average, NOAA noted. “The first part of the year was marked by extreme warmth in the West and cold in the East, but by the end of 2015, record warmth spanned the East, with near-average temperatures across the West. This temperature pattern resulted in every state having an above-average annual temperature.”
The report showed that December 2015 was record warm for the contiguous U.S., with a temperature of 38.6°F — 6.0°F above the 20th-century average. This broke the previous record of 37.7°F set in 1939, according to NOAA. Record warmth engulfed the eastern half of the nation, where 29 states had the warmest December on record. Near- to below-average December temperatures were observed in the West, and no state was record cold.
Average precipitation for the contiguous U.S. was 34.47 in. — 4.53 in. above average — and 2015 ranked as the third wettest year in the 121-year period of record. Only 1973 and 1983 were wetter, NOAA said.
“The central and southeastern U.S. were much wetter than average, while parts of the West and Northeast were drier than average,” NOAA said, adding that the national drought footprint shrank about 10% during the course of the year.
The December precipitation total for the contiguous U.S. was 3.93 in. — 1.58 in. above the 20th-century average and surpassing the previous record of 3.76 in. set in 1982 — with 23 states being much wetter than average. Iowa and Wisconsin had a record-wet December.
According to the Dec. 29 U.S. Drought Monitor report, 18.7% of the contiguous U.S. was in drought, down from 20.6% at the beginning of the month.
“Drought conditions dramatically improved across the Pacific Northwest, where record and near-record precipitation was observed during December,” NOAA reported. Drought also improved in parts of the Central Plains and Upper Midwest but expanded in parts of the Great Lakes and Northeast.
In 2015, there were 10 weather and climate disaster events, each with losses exceeding $1 billion. These events included a drought, two floods, five severe storms, a wildfire event and a winter storm. Overall, the events resulted in 155 human deaths and had significant economic effects. Further cost figures on individual events in 2015 will be updated when data are finalized later this year, NOAA said.