Final answer:
The most important factor determining the effectiveness of evaporative heat loss is the relative humidity of the environment. Other factors such as surface area, air mixing, and temperature also play a role.
Step-by-step explanation:
The most important factor determining the effectiveness of evaporative heat loss is the relative humidity of the environment. Evaporation occurs when water molecules change from a liquid to a gas, taking with them a great deal of energy from the skin. In environments with low humidity, more sweat evaporates, resulting in a greater cooling effect on the body.
Other factors that can affect evaporative heat loss include the surface area of contact between the air and the water, the degree of mixing (convection) of the air above the hydrated surface, and the temperature. However, relative humidity plays a significant role in determining the overall effectiveness of evaporative heat loss.