How hot is too hot to bike outside?

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In summer, the hot temperatures can make your cycling journey difficult, and even dangerous for your health. You might wonder how to determine when it’s best to give up on cycling and to avoid exercising in the heat.

Above 100°F (38°C), it is too hot to ride outside in direct sunlight, even in dry heat. Actually, above 90°F (32°C), you should be extra careful depending on the humidity, the time of the day, the distance to travel, the amount of water you can carry… and how accustomed you are to the heat.

In this article, we will see in more detail what’s the risk to cycle in hot weather and how to determine when it’s too hot.

What temperature is too hot for biking?

It is difficult to give a specific temperature that can be considered too hot for biking. It depends on several factors but as a rule of thumb: above 100°F (37.8°C) it is too hot to ride outside with direct sunlight and above 90°F (32°C) you should take some precautions before going out.

I mentioned that “several factors” affect the temperature which can be considered too hot to ride outdoors. This is the list of factors I was referring to:

Percentage of relative humidity
Wind speed
Time of the day
Duration of the ride
Distance to travel
Shade / Sunlight where you will ride
Amount of water you can carry or procure yourself on the way
How accustomed you are to the heat
…

The most important thing here is to understand that heat is not only related to the air temperature but also to the relative humidity and the wind speed. This is what is generally called the “feels like” temperature, which takes into account the combination of these parameters to give how a value that’s more representative of what the temperature feels like to your bare skin.

In the chart below, you get a feel of how the temperature is affected by relative humidity. You should consider that if the heat index is dark yellow, it is essential to take some precautions before going outside. If it is in orange, it starts being dangerous for your health. You can still go out but at your own risk! This is where I would draw the limit. In red, just don’t: you are really putting yourself in danger. It is likely to do a heat stroke at such temperatures.

Legend:

Caution: Fatigue possible with prolonged exposure or physical activity
Extreme Caution: Sunstroke, muscle cramps, or heat exhaustion possible with prolonged exposure or physical activity.
Danger: Sunstroke, muscle cramps, or heat exhaustion likely. Heatstroke possible with prolonged exposure or physical activity.
Extreme Danger: Heat stroke likely.

I explain the differences between heat exhaustion and heat stroke in the next cha.

Is it bad to cycle in hot weather?

The dangers of cycling in hot weather are as follows:

Sunburn

Getting sunburn is dangerous as everyone knows it. It can cause severe damage to your skin and increase your chances of getting skin cancer.

Dehydration

When you ride in the sun, your body will start to overheat and start sweating more than usual. This leads to dehydration. You can fight it by drinking more fluids than usual and more regularly. It is important not to drink only water but to take on some salts (and electrolytes) to compensate for the minerals you are sweating away from your body.

Heat exhaustion

This generally happens if you start getting dehydrated and struggle to cool down your body under the heat. Symptoms are dizziness, nausea, and a feeling of tiredness. If this happens to you, stop riding, and find a cool place to rest. If you can, it is best to lie down in a bath of water at ambient temperature to help your body hydrate and cool down. Do not put cold water: the shock might be dangerous for your body.

Heat stroke

This is the next level of heat exhaustion. Your body can’t take it anymore and these are the symptoms:

feeling unwell even aftertaking a long rest in a cool place and drinking plenty of water
not sweating even while feeling too hot
a body temperature of 104°F or above
fast breathing or shortness of breath
feeling confused
having seizures
loss of consciousness
not responsive

Please be careful of heat strokes and call the emergencies if this happens to you or to your bike buddies.