It depends. A wet towel with a fan gives a small cooling boost through evaporation, but it won't meaningfully cool a whole room.
This is a real trick, not a myth, but people often expect it to work like a mini air conditioner, which it doesn't. It's a low-effort backup for a hot night, not a replacement for actual cooling.
Whether it does anything noticeable comes down to one factor most people don't think about: how humid the room already is, since the whole effect runs on evaporation.
As water evaporates off the towel, it pulls heat from the surrounding air, similar to how sweat cools your skin. A fan blowing across a wet towel speeds up that evaporation and pushes the slightly cooler air toward you.
In dry climates or low-humidity rooms, evaporation happens fast and the effect is noticeable, sometimes a few degrees near the airflow. In humid rooms, the air is already close to saturated, evaporation slows way down, and the towel mostly just adds dampness without much cooling.
Block sunlight with blackout curtains or blinds during the day, cross-ventilate with two fans (one pulling cool outside air in, one pushing hot air out), run fans in the evening once outside temperature drops below inside temperature, and use a dehumidifier if humidity above 60% is part of the problem.
The wet towel trick is a real but minor assist, worth using in a dry room as a stopgap. For a genuinely hot room, blocking sunlight and improving airflow will do far more than a damp towel ever will.
An ice pack in front of a fan often cools the immediate airflow more noticeably and for longer, but both are minor, short-lived tricks compared to real air conditioning.
Yes, especially in an already humid room with poor airflow — the water just adds moisture to the air without enough evaporation to offset it.
Damp enough to feel cold and heavy but not dripping. A soaked, dripping towel adds excess moisture to the room without improving the cooling effect much.
Only if air is actively moving through it, like a breeze or a fan pulling outside air in. A still, wet towel with no airflow does almost nothing.