Heat, humidity and another tropical storm are expected for the end of the Olympics

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By Allison Chinchar and Taylor Ward, CNN Meteorologists

Heat, humidity and tropical systems have been the nemesis of athletes during these Olympic Games, and the closing weekend will bring more of the same.

While heat and humidity in July are common, these levels were above average. Tropical systems can also happen in July, but traditionally the peak months in Japan are August and September.

Organizers tried to help athletes to escape the heat and humidity by shifting venues and event times for the first few weeks, but it will still plague the upcoming marathon.

Heat and humidity: a critical combination

It’s not just the temperatures but also the humidity. When both are high, conditions can be oppressive for athletes.

When your body gets too hot, you sweat to cool off. But if the sweat cannot evaporate, the body cannot regulate its temperature. You need evaporation in order to effectively cool your body.

When the relative humidity is high, the rate of evaporation from the body decreases, according to the National Weather Service. In other words, the human body feels warmer in humid conditions.

To find cooler temperatures, the Olympics marathon events are taking place this weekend in Sapporo.
Sapporo, about 500 miles north of Tokyo, can be as much as 40 degrees Fahrenheit cooler.

But the high temperatures hitting Tokyo are spreading throughout the entire country. It will be cooler in Tokyo on Saturday than in Sapporo. Due to rain in the forecast, Tokyo’s high temperature Saturday will be 88, and Sapporo’s will be 93.

The women’s marathon takes place Saturday morning while the men race Sunday. This weekend Sapporo will see morning low temperatures of around 77 and afternoon highs of 90 to 93. Theses temperatures are 9 to 13 degrees above normal.

Temperatures during both races will likely be between 80 and 86 degrees. 80-86° F). Relative humidity of 70% to 80% will make it feel warmer.

Organizers moved the start of the women’s race an hour earlier, to 6 a.m., to avoid the heat.

“Athletes’ health and well-being are the organisers’ top priorities. Having taken advice from World Athletic’s medical team and reviewed all other considerations, World Athletics (WA), the International Olympic Committee (IOC) and the Tokyo 2020 Organising Committee had a series of discussions today and confirmed the schedule change,” a Tokyo 2020 statement read.

But will that one hour make a difference? Sunrise in Sapporo is around 4:30 a.m. now. With the race starting at 7 a.m., the sun will have been up for 2.5 hours before the race starts.

For comparison’s sake, let’s say you’re a runner who tries to beat the heat with an early workout in Atlanta, where sunrise is around 6:50 a.m. This would be like doing your workout between 9:30 a.m. and 11:30 a.m. — not exactly the ideal time to be running.

The only temperature relief may come from a tropical storm that will dump buckets of water on athletes this weekend.

Tropical storm to impact Tokyo this weekend

The Olympics have already been plagued by one tropical system when Nepartak made landfall during the first week. Now another, Tropical Storm Mirinae, is set to impact the final weekend. Events such as rowing were postponed two days due to the storm.

The center of the storm is expected to pass just southeast of Tokyo on Sunday morning.

For now, it looks like the majority of the rain will be Saturday night into the first half of Sunday. Some showers and scattered storms could linger into the evening for the closing ceremony. Winds will be a bit gusty, especially the first half of Sunday, but it shouldn’t be too bad as Mirinae is expected to remain a mid-range tropical storm.

The Closing Ceremony takes place Sunday at 8 p.m local time (7 a.m. EDT).

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