40" of rain isn't really all that much. It is not about how much you get, it is when you get it.
Just look at what you just said, below normal in May, dry in June and July and little in August. That sounds like a dry spell to me.
These things, thrips, aphids, spider mites, false spider mites, mealy bugs, and scale can almost explode overnight in terms of numbers. They are kind of born pregnant, live hard and die quick.
They can easily escape early detection if you are not looking. Sprays can offer some control. But if you kill 90% of them in a first spray by missing some hiding here and there, that population can build up and explode quickly.
This is exactly why I try to feed the birds, so many eat insects, and I welcome spiders. They probably eat more nuisance insects then we could ever hope to kill. So much
Of gardening is a delicate ballet where everything is in sync. Dry spells upset that sync and that's when insects explode!
