Every day the weather man on the news tells you today’s temperature is way above or below “normal.” They point to the average, and let you assume that number is what the temperature that day is supposed to be. It isn’t. It’s too simplistic. But the scary graphic with the crazy amped up color schemes gets the public in a froth and concerned about their impending doom.
I pulled 135 years of daily temperature records from NOAA for Gainesville, Georgia, going back to 1891, to illustrate the way weather should be reported. The Gainesville weather station has recorded a high and low temperature for nearly every single day since October of that year. What I found is the average temperature for any given date is close to meaningless on its own, and reporting it without context is how you mislead the public.
The Average Doesn’t Represent What the Temperature Should Be
An average takes every recorded high for a specific date across every year on record and divides by however many years you’ve got. For February 14th in Gainesville, that comes out to 54.3 degrees. It sounds logical at first that the average temp on the same day over the past years is a temperature that day is supposed to hit. And 54.3 is in fact within the normal range for that date. But it’s not what the temperature is supposed to be. Does anyone honestly think that any particular day has a precise temperature that it should be?
A better way to report this is to think about how much the temperature moves around from year to year. For example, February 14th has swung from a low of 9 degrees in 1899 to a high of 79 degrees in 1951. A 44 degree high on that date would be 10 degrees below the average, and a local weather man might say, “colder than normal,” making you think that day is out of the ordinary. But 44 degrees isn’t unusual for a mid-February day in north Georgia. It’s well within the range that date has produced dozens of times over the past century. The temperature range shows it’s just another February day.
What Should Replace the Average: Standard Deviation or Temperature Range
The solution is to use the standard deviation, which measures how much a given date’s temperature typically swings, calculated from every year in the record instead of the average. For February 14th, the standard deviation, or temperature range, of the historical highs is 11.5 degrees. That means a typical high for that date runs from about 43 to 66 degrees, a range built from the whole dataset. A reading of 44 degrees sits right at the lower edge of that band, but nowhere close to the “10 degrees below average” a typical weather report makes it sound like.
Now look at July 27th, where the standard deviation is only 4.6 degrees. Looking at the chart above you can see the temperature ranges in the summer time are much tighter than any other time of the year. The typical band for that date runs from about 84 to 93 degrees, only a 9 degree temperature range. A 79 degree high on July 27th is actually a departure from the range of temperatures that date normally produces. The standard deviation or temperature range gives you the complete picture.
We Need Honesty in Reporting
In today’s histrionics about climate change and how it’s going to destroy the world, it’s more important than ever to report the weather without hyperbole. Right or wrong, weather reporting shapes how people think about climate. When every normal day gets reported as “way above normal,” people believe it. A standard deviation or temperature range based system is the solution and an honest way of reporting. Instead of “10 degrees below average,” a forecaster would say, “near the low end of the typical range for this date” or “outside the typical range, unusually cold.” Reporting the weather in this manner, as well as taming the extreme colors used on today’s weather maps, would report the truth rather than whipping people into a panic.
NOAA has decades of daily station data sitting in public archives right now. If I can get the data and run that through an AI to get the temperature range chart you see above, then anyone can. If only anyone were interested in more than propagating hysteria.
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