December 2019 Repeats December 2018's Wet Conditions

 

 

December 2019 was the wettest month of the year and fifth wettest December on record (7.09" was measured).  Much of its precipitation fell in the first two weeks of the month.  In fact, the 5.05" that was measured during this period was the third greatest amount to fall in the first two weeks of any December.   Looking at temperature, the month was slightly above average (+0.8°).  Although Dec. 1-22 was 2.5 degrees colder than average, the rest of the month was mild enough (+9 degrees), to push the entire month into the above average column.  The mildest reading of the month was 58° (on 12/10), making this the first December since 2005 not to have any readings of 60° or warmer.  The coldest reading, 16° on 12/19, was three degrees colder than the typical coldest reading of December.  The 19th was also the only day that had a high of 32° or colder (25°).

 

Despite the month's surplus precipitation there were ten consecutive days with no measurable precipitation (Dec. 19-28).  This matched a 10-day stretch in September - the longest dry spells of the year.  (September 2019 had just 0.95" of rain, making it the eighth driest September on record).  Coincidentally, last year's wet December (ninth wettest) also had a ten-day stretch with no precipitation.

 

Being the wettest month of a year is rare for December.  Before 2019 only two other years had December as their wettest month - in 1957 (when 5.26" was reported) and in 1973 (9.98" was measured).  Another distinction for Dec. 2019 is that it was just the 13th month to have more than seven inches of rain as well as a streak of 10 or more days without any measurable precipitation.  (The longest streak during one of these months was thirteen days in June 2006).

 

In addition to the soggy first two weeks, other December highlights included the season's first measurable snowfall on 12/2 (1.3" fell) and an out of the ordinary snow squall of 10-15 minutes during the afternoon of 12/18 that ushered in the coldest weather of December (0.4" accumulated, and an additional 0.3" fell from a snow shower a few hours later).  Additionally, the first four days of the month had highs/lows stuck in the 30s, just the sixth time there's been a streak of this length or longer.

 

 

Finally, December 2018 and 2019 joined December 2008 and 2009 as the second pair of consecutive years to be among the ten wettest Decembers (2009 is #4; 2019 is #5; 2008 is #9; and 2018 is in tenth place). 

Previous December recaps:

2018

2017

2016

2015

 

 

Comments

[William]

Since the month had seven days with highs and lows in the thirties, did this set a record (or at least get close to a record) for the December with the smallest diurnal variation in temperature?

[Rob]

No, it wasn't a record. Just two years ago the variation was lower, and since 2000 there were seven Decembers with smaller diurnal variations, ranging from 9.3 to 10.3 degrees (Dec. 2019's variation was 10.4).

[William]

if December is the month that is least likely to be the wettest month of the year, then what is the month that is most likely to be the wettest month of the year?

also, what is the month that is least likely to be the driest month of the year and what is the month that is most likely to be the driest month of the year?

[Rob]

August is the month most likely to be the wettest for a year, followed by July (26 and 21 years, respectively); October and September are most likely to be the driest (23 and 18 years, respectively) and April is the least likely to have this distinction (5 years).