Where people go, poison ivy follows. It thrives in disturbed areas like empty city lots, roadsides, and at the edge of woods. Poison ivy is a people plant. In all probability, there's more of it today than in the past.
People can get it all year round.
The chemical isn't destroyed by freezing that is, it's still in the vine in the winter months. The weed along with its close cousins, poison oak and poison sumac belongs to the cashew family, whose tropical and subtropical members include the mango and pistachio. For all its ubiquity, poison ivy is often misidentified. The leaves of young box elder trees look similar, as does Virginia Creeper. The oily resin in poison ivy that produces the rash is incredibly long-lived.