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.