Quick Facts:
| Ave | 10Y | Low (Year) | High (Year) | |
|---|---|---|---|---|
| HLA | 53.81 | 52.87 | 47.50 (2013) | 64.52 (2021) |
| Highs | 81.15 | 81.20 | 74°F (2014) | 87°F (2010) |
| Lows | 25.77 | 25.90 | 13°F (2022) | 32°F (3x) |
| Precip | 1.61” | 1.72” | 0.04” (2021) | 4.86” (2018) |
December HLAs
This chart shows the trend in temperature averages, 2010-21. The horizontal line is the 10-year average for December.
Copyright © 2021 by Chan Fry. Some rights reserved.
December Temperatures
December’s temperature average is 53.81°F, making it our third-coldest month behind January and (barely) February. Three of the past twelve Decembers were colder than the same year’s January, and four of them were colder than the January that immediately followed. The warmest December on record was in 2021, with an HLA of 64.52°F, beating the previous record (2012) by more than seven degrees. I couldn’t find when the coolest December was, but the coolest recent one was in 2013, averaging 47.50°F.
According to a variety of sources I searched, the coldest temperature ever recorded in December was 5°F, on Dec. 24, 1989, but the coldest December day during my 13 years of record-keeping was 13°F on Dec. 23, 2022. The warmest temperature December has ever seen was 87°F, on Dec. 21, 2010. Only three daily record lows occurred during the past 12 years, while nineteen daily record highs belong to the same 12-year period.
December (like January) never hits the 90°F mark. Every December reaches freezing at least once; we average four days per December that reach 32°F or cooler (as many as 14 in Dec. 2013, but as few as one, in 2015, 2018, 2019, and 2021). Only three times in ten years has the high dipped below freezing.
December Precipitation
This chart shows December’s precipitation, 2010-21.
Copyright © 2021 by Chan Fry. Some rights reserved.
Precipitation
Rainfall in December is less variable than most months. It’s among our driest months (along with July, November, and February) and is below the all-month average most of the time. Most Decembers see fewer than two inches of rain and the average is 1.72 inches.
December averages 8.58 days per month that exhibit precipitation — above average — which means that most of those rainy days do not see much actual rain.
Trends And Patterns
In the 13 years I’ve been keeping track, December’s temperatures have jumped up and down regularly, and does not match well with the yearly average or other months. In 2021 we saw an unusual (absurd, even) jump in December temperatures, and it was the first time December averaged warmer than the same November (in fact, it was warmer than most Novembers). At the same time, the year average was below normal.
December’s rainfall tends to decrease when temperatures rise, but it isn’t a perfect correlation. It does match well with the yearly averages. December is usually wetter than average when the year is, and drier than average if the year has been. (Exceptions were 2010, 2011, and 2021.)