I worked as part of a watershed project for the area, cedar gnats generally come out during warm months. We do have a lot of tamarisk beetles. They are consuming the non native species of trees. If you visit the park, you'll see some dead russian olive trees and tamarisk trees and thank the yellow and green stripped beetles that land on you. They are harmless, and a friend of watershed projects!
Yes they come out when it's hot.
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