As the water droplets scatter light, they appear white and you can see your breath. The warm lake warms and moistens the air directly above the lake. As cool air blows over the lake, it mixes with this warm, moist air, bringing the air over the lake to saturation. Recall figure 5.11 from page 118. As warm air mixes with colder surrounding air, it follows a linear path from one point to the next.
Humid air is actually lighter than dry air.
Michela feels less comfortable in New Orleans because the air is much more humid in New Orleans than in Phoenix. Our body cools off through evaporation of sweat. Recall that it takes energy for liquid water to evaporate, so energy that would ordinarily be used to warm our body is now used to evaporate sweat. As Phoenix is much dryer than New Orleans, more evaporation will take place in Pheonix. So, even though it is warmer in Phoenix, Michela feels cooler due to the latent heat of evaporation.