Nighttime is often the best time to find cicadas.
Nymphs, generally speaking, emerge soon after sunset. When I look for nymphs, I wait until sunset and start looking around tree roots and on tree trunks. Sometimes it takes hours, but usually, I find one (or many).
Adult cicadas are easiest to find on hot, humid nights in well-lit areas like parking lots and the sides of buildings. You will find them clinging to illuminated walls and crawling on sidewalks. They end up on the ground, often because they fly into the wall and stun themselves. On a hot humid night — 85F or above — I’ll find an excuse (usually frozen desserts) to check the walls of the local supermarket for cicadas.
Cicadas, like many insects, are attracted to (or confused by) lights. There are many theories as to why insects are attracted to lights, and the reasons why probably vary by species. My guess (and this is just a guess) is that cicadas can’t tell day from night, or daylight (sun) from artificial lights, and so they think they’re using light to navigate away from a dark area (a tree trunk, dense brush), and then get very confused because they never seem to get anywhere once they reach the source of the light. I wish I could ask a cicada why.
If you go looking for cicadas at night, make sure you have permission to be where you plan to look. Don’t trespass, and have respect for other people’s property.