December 2020 Weather Summary
December was a lot warmer and a little bit drier than normal. The warmer than normal continued a trend that started in November but the drier than normal has been occurring on since September.
Two cold snaps in December tempered the above normal temperatures, but not by much. The average daily high for December was 46.6, 5.6 degrees above normal. The average overnight low was 24.9, 3.7 degrees above normal. This gave us a monthly mean temperature of 35.7, 4.6 degrees above normal. The highest temperature for the month was 67 on the 9th and again on the 22nd. The lowest temperature for the month was the low of 11 degrees on the 23rd and 24th. There were three records set during December. The high of 67 on the 9th broke the old record high for that date. The previous record was 66 set in 2015. The high of 67 on the 22nd also broke the record high for that day. The previous record was 65 set in 1950. The overnight low of 39 on the 21st broke the old record high low temperature of 37 set in 2014. While it was a warm December it wasn’t record warm. The warmest December on record was in 1957 when the area had a monthly mean temperature of 40.2. The coldest December was the bone chilling December 1983 when we had a monthly mean temperature of 13.6. Christmas 1983 broke clear and cold with a low of -12 but after only reaching a high of 1 degree on the 24th the mercury did climb clear up to 17 on Christmas Day! Nearly as cold was December 1989 when just ahead of Christmas we went nearly 72 hours with the mercury never climbing above zero!
The only significant precipitation for December occurred in a mixed precipitation event just before the end of the year. Normal December rainfall is 1.02 inches. Milford Lake received 0.77 inches for the month and Junction City 0.91 inches. Only a trace of snow fell for the month, normal is 3.7 inches. Season to date the Junction City area has received 0.3 inches of snow, normal season to date is 4.7 inches of snow.
In meteorological circles 30 year averages are frequently used for “normal” and these 30 year averages are recalculated every ten years. 2021 we start using new “normal” or average precipitation and temperatures based on the period from 1991 - 2020. In general the new normal temperatures are slightly warmer with low temperatures rising more than high temperatures. Over the past ten years we will have seen the annual mean temperature rise nearly six tenths of a degree. The average daily high rose two tenths of a degree but the average overnight low rose one full degree. Average annual rainfall increased slightly from 33.15 inches to 33.56 inches. In general late summer, fall and winter monthly rainfall declined slightly while April through August precipitation increased.
January is historically or coldest and driest month of the year but along with February, it’s our snowiest month. Average daily highs start on New Year’s Day at 38 and by the end of the month are up to 42. Average overnight lows range from 18 on the 1st to 20 on the 31st. January is our driest month of the year with only 0.73 inches of liquid precipitation but ties with February for being the snowiest month with long term average January snowfall of 4.7 inches.
2020 Weather Summary
2020 was very much a mixed bag of weather. It was warmer than normal and depending on where you were in the area, slightly drier than normal or slightly wetter than normal!
The annual mean temperature for 2020 was 55.4, 1.1 degrees above normal. The average daily high of 65.6 was right on target for the long term average daily high but the average overnight low of 45.3 was 2.3 degrees above normal. There were 7 months with average temperatures above normal and 5 months below normal. The hottest day of the year was August 8th with an afternoon high of 96 degrees. The coldest morning of the year was February 13th when we had a morning low of 2 degrees. This is the second year in a row we failed to reach the century mark. It is, however, the first year since 2015 that we didn’t dip below zero. The 94 degree temperature extreme range is well below the long term average of just over 109 degree average annual temperature range!
Annual precipitation at Milford Lake in 2020 was 34.04 inches, slightly above the normal annual precipitation. Junction City received 30.43 inches of precipitation about 3 inches below normal. Most of our precipitation will normally fall from April through August when we expect to receive 65% of our annual total. Milford Lake received 72% of their annual total in those five months and Junction City received 67%. While the Milford Lake rainfall total was above normal for the year, only 4 months in 2020 had above normal precipitation with the other 8 months being below normal. The 2019-2020 snowfall season was only about 3/4 of normal. Long term average seasonal snowfall is 18 inches and we received 13.5 inches. December 2019 was the snowiest month of that season with 7.5 inches of snow. The snowfall season runs from October to May.