Visibility Activities
The best thing to do is to investigate an aspect of your local environment which is affected by visibility problems.

Why not try to find out about frost hollows, or an area which is particularly prone to fog in the evenings. Then measure the temperature and humidity throughout the afternoon and into the night. Calculate the dewpoint too.

What does this tell me?
Compare the readings with a contrasting area nearby; flat ground or the top of a hill. You can find out what kind of fog this is and at what temperature it forms. Is it related to a water source such as a river or lake, or to a warm city centre.