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2018, reviewed: Another top-5 warm year, and more numbers

/ January 3, 2019 at 8:30 AM

Despite January’s frigid start, 2018 landed within the top-five warmest years on record at the airport, tying 1998 with an average temperature of 67.9°. This is the fourth consecutive year that average temperatures have landed within the top five warmest on record. 1990 still reigns supreme, though, as the warmest recorded year with an average temperature of 69.3°.

Data for this post is sourced from a compilation of records by the Southeast Regional Climate Center as well as the National Weather Service forecast office in Charleston, SC. Records at the North Charleston climate site begin in 1938.

Some other notable temperature tidbits from 2018:

Precipitation

2018 climate plot for the Charleston Airport climate site.
Source: National Weather Service, Charleston, SC Weather Forecast Office

The Charleston area started the year in moderate drought. This quickly changed in mid-May as a period of very heavy rain inundated the Charleston area, sending rainfall well above normal and keeping it there through the summer. We started to slip back into drought as we got into September and October (despite two tropical systems!) before ending the year on a very wet note.

Some precipitation numbers:

Trends

Temperatures

Average temperatures by year at the Charleston International Airport.

Yes, it’s getting warmer, both locally and around the globe. Since 1938, the trend in average temperature has been undeniably upward, ticking up some 2.5° when looking at the regression line above. As mentioned earlier, for the fourth consecutive year, we have set another top-five temperature record.

Annual sum of cooling degree days as figured from data at Charleston International Airport.

This warmth has had impacts on energy bills. (So has a certain nuclear plant, but that’s beside the point.) Looking at cooling degree days, which sums how many degrees the average temperature exceeds 65°, you’ll see that we’ve set two record highs in the last three years. In fact, 2018’s CDD value of 2920 is second only to 2016’s 2965. This has real economic and infrastructure impact, and is something to watch closely, especially as we plan resilience efforts to impacts from climate change.

Precipitation

Annual total precipitation at Charleston International Airport.

Precipitation trends are less clear. Any attempt at calculating average is going to be skewed wildly by 2015, so it is hard to extrapolate from here. For what it’s worth, removing 2015 shows a much flatter trend as far as precipitation goes.

Generally speaking, a normal year of precipitation in Charleston is around 51.03″ of rain; with 57.69″ in 2018 (driven largely by the excessively wet months of May and December), we exceeded that average, and have done so every year since 2013.

It’s also important to note that when looking at one climate site for precipitation, it won’t tell the whole story — that’s just a point. Many places got much more rain than the airport this year, such as CoCoRaHS station SC-CR-87, which received a very impressive 75.87″ in 2018.

While it is nearly impossible to predict with certainty what 2019 holds, we’ll want to watch temperatures and any possible link to enhanced or lowered precipitation totals closely this year and in the years to come.