The city with the least amount of water vapor in the air is City B. The city with the greatest amount of water vapor in the air is City A. The city with the lowest relative humidity is City B. The temperature to which you would need to cool City C to reach 100% humidity is 21 degree F. To reach the same relative humidity as City A, the temperature of City D would need to rise by___degrees.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.