Before his 2021 retirement, longtime 95.5 WSB meteorologist Kirk Mellish used the Mellish Meter to grade an Atlanta day’s overall weather. A “10″ was reserved for that ideal day of medium warmth, little to no wind, and crystal-clear skies. “1″ days were for straight up severe weather.

In Atlanta’s volatile and sensitive traffic environment both “1s” and “10s” are, maybe surprisingly, dire for those hoping to make good time.

A day that invites the masses to enjoy the Earth’s warmth and comfort puts more autos on the roads. Discretionary car trips dramatically increase, as people range from running errands to finding perfect places of leisure. Even on workdays, more people that have the option are likely to head to the office, and to lunch, or to something fun afterwards.

So more people hit the roads in stunning weather. What a breakthrough. But there is is more to it.

Clear skies mean that sunshine delays are even more intense adjacent to sunrise and sunset. These are underestimated, as the distraction of the bright sun not only causes traffic to slow, but can also hamper visibility nearly as much as fog does. And, as luck would have it, the sun’s angle is the worst during morning and afternoon rush hours.

God has to have a sense of humor, right?

Sunny days, especially midweek, make for rush hours with heavier peaks of delays. And “10s” also drive more folks to driving in their free time on weekends. Even if the crash count is low, which is not a guarantee, the sheer amount of volume can create for grueling delays on the roads in perfect weather.

“1s”, of course, wreak havoc on traffic. Copious rain causes spinouts left and right. Heavy wind knocks out power and topples trees and wires. And any hint of snow and ice - well, we have seen what that can do. Horrible weather days take some of the bite out of the amount of vehicles on the road, but increases the crash rate for those that remain in the elements.

In an internet search of the worst car crashes in U.S. history - the ones with the most vehicles involved and most people hurt - every single one involved inclement weather. Most involved heavy fog, which is an underrated danger on the weather spectrum. Heavy rain and wintry conditions also factored into some of the other melees. One crash in a southern state, to the point of sun’s influence on traffic, was triggered by the heavy glare on the wet roads after a heavy rainstorm. Stopping power and visibility - those matter.

That glare phenomenon is seen during summer afternoons in Atlanta, when popup storms plow through and the sun immediately replaces them. That leaves behind some dicey driving conditions.

The ideal travel weather does not match up with Mellish’s scale. Cloudy, dry, and cool is the recipe for the best traffic stew. Cloudy and cool reduces the amount of people traveling. Cloudy conditions keep Mr. Golden Sun under the covers and eliminate those delays and visibility concerns. And dry pavement, of course, maximizes the grip, whereas a rain or snow storm lessens it.

Pray for a cloudy day with the threat of severe weather that does not actually materialize and make it on a Monday, when people often stay home and stretch a weekend. This is the absolutely ideal kind of weather day to take the bite out of delays on the streets.

Weather and traffic are usually sympatico. But their paths diverge when weather is so good that people want to take advantage. A traffic “10″ is cloudy and cool. The groundhog emerges.

Doug Turnbull, the PM drive Skycopter anchor for Triple Team Traffic on 95.5 WSB, is the Gridlock Guy. Download the Triple Team Traffic Alerts App to hear reports from the WSB Traffic Team automatically when you drive near trouble spots. Contact him at Doug.Turnbull@cmg.com.

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