The temperature of a riders scalp when wearing a helmet depends on a few different factors. To name some main factors we have:
A) The temperature of the riders environment (Weather conditions, indoor outdoor riding etc.)
B) The body temperature of the rider (Activity level of the rider)
C) The ventilation of the worn helmet (Compare modern vented helmets to the classic non vented velveteen helmets)
Riding with a high level of activity and on a hot day will naturally make you feel hotter than a moderate ride on a cool day. So if you wear a helmet with good ventilation that allows air to circulate around your head, you should not feel significantly hotter because of your helmet.
Riding can be dangerous. Like with any physical activity, riding during hot or cold temperatures may increase health risks. If you are not sure if it is safe for you to engage in physical activity, please ask a health professional.
