I am not sure what drives fire flies to get active, but they are starting to visit my area. I had seen sporadic ones over the last week, but last evening they were out in numbers. They so seem to appear in hot and humid conditions, so the next few nights may be real interesting. The typical place I see them are in fields and along right of ways. It has been awhile since a "peak" year for them but at least one year, the right of way in front of my house was lit up in either direction by them.