At higher temperatures, when air particles are farther apart and moving faster, a lot of water vapor particles can fit in between. There's your white cloud above the tea kettle. The amount of water vapor actually in air as opposed to how much the air is capable of holding is called relative humidity. The hotter it gets, the more water can fit into the spaces between air particles. A psychrometer or a hygrometer is used to measure relative humidity.
Evaporation is a cooling process.
A wet surface covering the bulb end of a thermometer will cool as water evaporates from it into the air. The drier the air, the faster the evaporation and the cooler the wet bulb will become. The wetter the air, the slower water will evaporate into it and the wet bulb's temperature is not lowered as much. Punch a hole in the side of the bottle about an inch from the bottom. Heating the awl will make a perfect hole.