Five years of sick-leave records all point to one date on the calendar. And weather offers a pretty good explanation.

On Monday, someone in America will call in sick to work. And statistically, they will have picked the most popular day of the year to do it.

America's sickest day

Aug. 24 tops five years of sick-leave records as the single most common day for U.S. employees to call out of work, according to an analysis by Flamingo. The company reviewed sick leave taken at larger employers and found the late-August date outranked every other day on the calendar for absences.

Which raises a question: why late August?

It's not from germs

If Aug. 24 were about actual illness, it wouldn't be in August at all. The same data shows February is the month with the highest share of workers out sick, which is peak flu season, so it makes sense.

And the second-ranked single day on the list? Feb. 13, which is notably right around Valentine's Day and the Super Bowl. Not suspicious at all...

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So two of the calendar's biggest sick days likely have nothing to do with being sick. They land next to something people would rather be doing.

The weather makes a pretty good case

For much of the northern half of the country, Aug. 24 sits in one of the most pleasant stretches of the entire year. The oppressive heat and humidity that defined July has begun to relent, and evenings are still long as the sun sets late in the evening.

Across a dozen major Northeast and Midwest cities, average high temperatures on Aug. 24 sit in the low 80s, with nights averaging the mid-60s. Warm enough for the lake but cool enough to sleep with the windows open.

Perfect weather to be lured away from a desk and towards the outdoors.

Studies have also found that the majority of workers find themselves less productive in the summer, mostly due to heat or trouble concentrating. So, even if you did plan to show up to work, you may not get as much out of it as you would have hoped.

The back-to-school squeeze

But the weather isn't working alone. Aug. 24 also lands in that last stretch of summer break for many, and notably in the same areas that the forecast turns pleasant. While many Southern districts are already back in session by then, much of the Northeast and Midwest doesn't start back until the last week of August or after Labor Day.

That leaves the perfect window for great weather, kids still home and a couple more good days before the backpacks come out.

So what do you plan to do on Monday?

Miriam Guthrie is an associate meteorologist with weather.com who graduated from Georgia Tech with her undergrad and graduate degrees in Earth & Atmospheric Sciences.