The periodical cicadas will emerge when the soil 8" below the surface reaches 64 degrees F. You may already see signs of cicadas nymphs making their holes/galleries in the soil now. They are moving up in preparation for emergence when the temperature is just right. UMD entomologists say we're still a couple of weeks away from the mass emergence -- possibly in early to mid-May. It really depends on the weather. If you find cicada nymphs near the soil surface (under rocks, boards) or when digging in your garden, a way to tell that they are almost ready to emerge is when they have black patches on their back (right behind the eyes) and their eyes are red. Here is more information from the UMD "Bug of the Week" blog.

http://bugoftheweek.com/?offset=<personal data hidden>29&reversePaginate=true

Put netting on your young trees when first you see the cicadas out flying, before the males begin to "sing." 

This page on our website has much more information. https://extension.umd.edu/resource/cicadas

Here is a video on how to net small trees.
https://youtu.be/X4vjivdnfMM

Christa