I have tried to find a direct answer to this, but it's very difficult as all results direct me to cancer conversations. Suppose that one is dealing with extreme temperatures and sun exposure; on a clear day swelling to high temperatures, what's more immediately dangerous - heat or uv? Is it safer in the shade if it's hot enough that the ambient temperature remains the same?

  • 1
    There is no circumstance where being exposed to direct sun will not be hotter than the shade.
    – Bryan Krause
    Jan 3 at 14:41
  • 3
    As a start you should look up Hyperthermia (AKA heat stroke), and this should give you an idea of how immediate the effects are for this vs UV. This is assuming normal UV and heat exposure from the sun rather than point sources of very high intensity as in SciFi.
    – bob1
    Jan 3 at 21:47

1 Answer 1


Heat stroke can be deadly and it can occur in a relatively short period of time, even under an hour.


When heat stroke occurs, the body temperature can rise to 106°F or higher within 10 to 15 minutes. Heat stroke can cause permanent disability or death if the person does not receive emergency treatment.

UV from sun exposure can be deadly, but only after years of exposure and/or multiple severe sunburns, and then only indirectly via the secondary cause of cancer.


Most skin cancers are a result of exposure to the UV rays in sunlight. Both basal cell and squamous cell cancers (the most common types of skin cancer) tend to be found on sun-exposed parts of the body, and their occurrence is typically related to lifetime sun exposure.

In short, no one dies of UV exposure from the sun in an afternoon, but people do die in an afternoon due to heat, making it easily more immediately deadly.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.