Climate Monday: Putting Recent Weather in Context

It snowed in Wooster today. It also snowed in Pennsylvania, Michigan, Iowa, Maryland, and several other states. Across the Northeast and Midwest, baseball broadcasters, news anchors, my coworkers, and even random people on the street are remarking on how “It sure doesn’t feel like spring”, and “why won’t winter go away.”  Actually, this refrain has been happening since a series of big storms pummeled the East Coast in March.  So of course I wonder: how uncommon has the late winter/early spring weather been?

I figure we can use this griping to highlight where to go to see past weather in context.  It’s all too easy to get a forecast for tomorrow, and it’s all too easy to complain that the weather “isn’t like it used to be”.  But let’s get critical here: Is this abnormal? Here’s a few places you can go to get an answer:

  1. Go to NOAA’s “Climate Data Snapshots“. You can quickly display the basics of climate (temperature and precipitation) for any month in the 21st century up to last month. There’s a few other options, too (like drought and climate change projections). Here’s their map for whether the USA was cooler (blue) or warmer (red) than normal last March:

So yes, the East Coast was a bit colder than normal, but only by a few degrees Fahrenheit in most places. Maybe people in eastern Montana had better reason to gripe about the weather than anybody in the Midwest or Northeast. In was 10°F colder than normal up there.

2. For a little more analysis, check out the NOAA News section. This week, they have the summary for March 2018. They provide some context in addition to the maps on this site.  They also use a different map for showing whether it’s been colder or warmer than normal.  This map is a percentile map; instead of showing how warm or cold compare to normal it was in °F, it asks, what percentage of Marches were colder (or warmer) than this one?


Here we can see that although eastern Montana was about 10°F colder than normal on average in March, that’s par for the course in Montana.  The temperature varies widely out there on the northern plains, so an erratic March is nothing new.  In North Carolina and Virginia, however, having a March that is 5 or 6°F colder than normal is something rare, so pockets of those states came in “much below average”.  In other words, just as the average temperature in Montana is colder than North Carolina, the temperature in Montana is also more variable than in North Carolina.

3. A third place you can go is to the professional weather and climate bloggers at Category 6 on Weather Underground. Bob Henson and Jeff Masters are more likely to put a personal spin on a story, but sometimes that’s even more interesting.  They often highlight NOAA’s maps and give their own flavor.  For example, they prefer to highlight the state-wide averages for temperature:

When you do that, the whole story of the East Coast be cold and snowy (and it was snowy, for sure) pops out even more distinctly than eastern Montana — because overall, the state of Montana was pretty average.  Some of the detail is lost for big states when state-level data are used, but they also have some appeal — it’s easier to think in states than the the divisions used in the previous two maps, after all.

So getting back to today, what do the numbers say for Wooster.  Well, Sunday April 8 was the coldest day recently, with a low temperature of 23.5°F at the weather station at the OARDC just south of town.  The record low for April 8 is 14°F, set in 1982.  The average is 33.0°F. So no, this wasn’t record cold for Wooster. But it was pretty low — only 12 years (about 10%) since 1900 had a lower daily minimum for April 8.  Also, of the 52 years with non-zero precipitation on April 8, a total of 11 of them had snow — that’s 21%.  (It drops to 19% for April 9.)  In other words, yes, it’s colder than normal…  and yes, snow is rare on April 9 in Ohio.  But not that rare.  The last time it did, in fact, was… 2016.

About acrawford

Alex Crawford is a climate scientist whose specialties include the development of Arctic storm systems, the seasonality of Arctic sea ice, and the interactions between sea ice, storm systems, and the Arctic Ocean. He primarily works with observational data (e.g., from satellites, weather stations, and compilations like atmospheric reanalyses) but also works with output from climate models.
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