From What Disability: (click for full article)
The recent heatwave has been blamed for the death of 35 people. Extreme heat can be more detrimental to those who's bodies are already affected by debilitating conditions. About 400 people die every year from heat strokes and many of them are elderly or disabled.
A heat stroke occurs when the body temperature rises causing the natural cooling system in our body to kick in. If this process cant get rid of the heat fast enough it will fail causing the vital body organs to heat up and eventually stop working, resulting in even more debilitating conditions or death.