Virtually no snow, temperatures 20 degrees above normal and records tied or broken all have made December’s weather something to remember for many people in the area.
La Niña, a climate pattern in the Pacific Ocean that can affect weather worldwide, is responsible.
“We are officially into a moderate La Niña,” said Logan Clark, meteorologist with the NWS in Wilmington. “Temperatures are, generally speaking, are going to be above normal in the Ohio Valley.”
High temperatures this month have been dramatically different from the 30-year average for the region, and they have broken or tied records this week in Dayton and Cincinnati.
On Monday, Dayton reached 66 degrees to tie the record high temperature for the day set in 2008 and 2015.
Cincinnati on Christmas Day broke a nearly 130-year-old record when the high temperature reached 69, shattering the previous record of 66 degrees set in 1893. It also marked the hottest Christmas Day since 1871, when records were first kept. This Christmas reached 61 in Dayton. It didn’t break the high of 65 set in 1893, but it was the fifth warmest Christmas on record.
The average December temperature in Cincinnati is expected to be higher than November’s average. This happened only two other times in the last 100 years, in 2019 and 1984, according to the NWS. December has never been warmer than November in Dayton or Columbus during that time.
For the month of December, there have been six days of temperatures 15 degrees or more above normal in Dayton and eight days in Cincinnati.
Those warm days have prompted some people to walk their dog while wearing short pants, get in a rare round of December golf, or, in the case of one man in Dayton on Monday, take a JetSki for a ride on Eastwood Lake.
It’s also been a wetter than normal December.
In Dayton, 3.86 inches of rain has fallen this month through Tuesday afternoon, compared to the normal 2.62 inches for December. With more rain expected later this week, the annual rainfall is expected to surpass the yearly average of 40.9 inches.
In Cincinnati, 3,03 inches of rain has fallen in December through Tuesday afternoon. This is so far below the average 3.24 inches for the month, but rainfall for the year of 49.51 inches as of Tuesday afternoon is well above the yearly average of 44.77 inches.
Snowfall for the month is 0.3 inches in Dayton, compared to the average of 4 inches. Cincinnati, which has a normal December snowfall of 3.4 inches, will end the month with 0.5 inches of snow for the fourth time in the past eight Decembers. That happened only four times in the previous 23 Decembers combined, the NWS said.
This is the second year in a row for La Niña. During La Niña conditions, trade winds in the Pacific Ocean are stronger than usual, pushing more warm water toward Asia. Off the west coast of the Americas, cold waters are brought to the surface in the Pacific that push the jet stream northward. This tends to lead to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada. During a La Niña year, winter temperatures are higher than normal in the South and cooler than normal in the North, according to the National Oceanic and Atmospheric Administration’s Climate Prediction Center — a division of the NWS.
“In Ohio, the pattern is above normal precipitation, above normal temperatures,” said Clark, who noted that the average high temperature will trend lower into the winter season.
“Some above-average snowfall is possible,” he said.
Temperature swings where the jet stream brings below normal temperatures to the region at times can be expected, Clark said.
The outlook for January, February and March gives Southwest Ohio equal chances of above-normal temperatures or below-normal temperatures.
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