The winter of 2017-2018 can be described by one word: wild. From record cold in January to record warmth in February followed by a cooler March — not to mention the four nor’easters that affected the Northeast in just three weeks — this winter will certainly be remembered. We’re going to breakdown the more notable events that have occurred month-by-month along with some climate statistics.
The average temperature in December for the contiguous U.S. was 34.8°F, which is 2.1°F above average. The greatest positive anomalies was in the Southwest while the Northeast, Great Lakes region, and portions of the Northwest were slightly cooler than average overall. The month actually began warmer than average for these areas, but the bottom dropped off beginning around Christmas Day to an impressive stretch of cold. In California, the record warmth and below-average precipitation added to the ideal wildfire conditions during the month with several devastating and record-breaking wildfires impacting southern parts of the state.
In terms of precipitation, the contiguous U.S. precipitation total for December was 1.55 inches, which is 0.80 inch below average. This was also the ninth driest December on record and driest since 1989, according to the National Centers for Environmental Information (NCEI). 15 states had much below-average precipitation, including much of the West, Central Plains, Midwest, and Mid-Atlantic. Meanwhile, portions of the northern Rocky Mountains and portions of the Southern Plains were wetter than normal, which correlates with where there is no current drought. Compared with the end of November at 6.6 percent coverage, the drought at the end of December was at 27.7 percent coverage. That’s 21.1 percent more coverage.
The end of December turned cold, and a several storm systems brought snow to the country leading up to Christmas, allowing for 49 percent of the contiguous U.S. to have a white Christmas. Portions of the Northeast even woke up to falling snow! A winter storm also affected much of the South after Christmas. A city like Brownsville, Texas received record snowfall, which we discuss in our “Winter 2017-18: Winners and Losers” article here.
January started off very chilly for much of the Eastern U.S.. Despite this cold start to the month for some, however, the average contiguous U.S. temperature was 32.2°F, which is 2.1°F above the 20th century average. The Western U.S. was the hotspot in January overall where nine states had monthly temperatures that ranked among the 10 warmest on record. Also more than 2,000 daily warm temperature records were broken or tied across the region. Meanwhile, much of the Eastern U.S. had a cooler than average January. More than 4,000 daily cold temperature records broken or tied across the East yet no state had a record cold monthly temperature, according to NCEI. The fact that the number of cold records outnumbered warm records is somewhat uncommon based on the fact that our planet is warming overall. The ratio of warm records to cool records since April of 2017 is at about 2:1. So for every two record high temperatures, one record low temperature occured.
The month of January helped to shape the current state of drought across the nation. Below-average precipitation was measured across 15 states with the greatest concentration in the Southern Plains. In fact, Alabama had its ninth driest January and New Mexico tied its 10th driest. It was a different story in the Central Plains and Northeast where above-average precipitation was recorded in these regions overall.
Snowfall this month was significant, especially in the South because a second snowstorm impacted parts of this region. On January 4, the Savannah, Georgia, airport received 1.2 inches of snow, the most since 1989. Then a different storm on January 17th affect areas to the west, including the northern suburbs of Atlanta where up to 10 inches fell, while the city of Atlanta measured a storm total of 2.4 inches. Unfortunately, it was a dry month for the mountainous regions out west. Tourism lacked in the Sierra Nevada due to the below-average snowfall. A similar pattern as December allowed for the drought area to grow to 38.4 percent by the end of January, up from 27.7 percent at the beginning of the month.
February 2018 was a rather warmer month than February for some areas, specifically the East Coast. The month as a whole ended up with an average temperature of 1.6 degrees above average for the Lower 48. For the eastern third of the nation, it was a warm February. According to NCEI, “eight states in the Southeast and southern New England were record warm and 15 additional states in the East had a top 10 warm February.” There were also more than 650 all-time monthly temperature records broken or tied. Meanwhile in portions of the Central US, temperatures were below average. Montana had it worst with its sixth coldest February on record with a monthly temperature 9.7 degrees below average, making it the coldest February for the state since 1989.
In terms of precipitation, one single storm system, lasting about one week long due to a stalled frontal boundary allowed for flooding and record rainfall for some areas from the Lower-Mississippi River Valley through the Ohio River Valley. There were six deaths reported due to these flooding rains. Six states ended up having their wettest February on record while ten additional states made the top ten list for most precipitation in February. The northern Rocky Mountains also had a wet, or in this case snowy, February. The combination of heavy precipitation and below-average temperatures resulted in record snowpack for some locations. This makes for a stark contrast to the situation in the Southwest. California had its third driest February on record with 13.5 percent of average precipitation. The snowpack in the Sierra Nevada was also well below normal. This below average precipitation in the Southwest allowed for a worsening in the drought while conditions improved in portions of the East due to the heavy rains.
March was the most wild month, especially for the Northeast, this winter due to the four nor’easters that formed, which is unprecedented. There isn’t much of a record-keeping for how many nor’easters occur and affect the Northeast in just one month, but four in one month is definitely very uncommon. Despite the cold and snow in the Northeast, the contiguous US overall experienced temperatures at 1.1 degrees above average. This month was not a record warm or cold March for any states. Instead, temperatures were below average for much for the East Coast while it was above average for much of the Southwest, Southern Plains, and Rockies. Some locations in the East actually observed March temperatures that were cooler than February, an unusual but not unprecedented occurrence.
In terms of precipitation, there were those four winter storms for the Northeast, which brought heavy snow, coastal flooding, beach erosion, and widespread power outages. “Some locations in the East had more snow during March than during the preceding winter months combined. Numerous locations had a top five March snowfall total during 2018, including Boston, Massachusetts; Albany, New York; and Philadelphia, Pennsylvania,” according to NCEI. Above-average precipitation finally affected most of California while it remained snowy in the northern Appalachians and into the Northern Plains. The Southwest remained very dry, on the other hand.
The month of April is soon to end. It was a very cold month for the Central US, specifically the Northern Plains and Midwest. Temperatures over a widespread area in this part of the country experienced temperatures over 10 degrees below average. That cooler than normal weather also extended toward the Gulf and East Coasts overall. Meanwhile, most of the West got to enjoy the warmer than normal weather. This significant chill that plagued a large region much of April will likely make this a cooler than normal month for the Lower 48, the first below average month this year.
April continued the very dry trend for the Southwest as well as into much for the Central US. Both Kansas and Oklahoma have not recorded a tornado during the January through April time period, which has never happened before. Farther east, much of the eastern third of the US experienced wetter than normal weather.