Yes, apparently.
We see someone in the bathtub be affected by the Swooping Evil venom. Their face goes blank in a way that implies the venom took effect. We also see people drinking water forget as well. There are also water collection tanks on top of the roofs.The wizards are seen fixing them along with the rest of New York. I'll check my copy of the screenplay for textual evidence. But yes, I'm guessing the venom got into the water supply somehow. So presumably, it would later affect people who were under an umbrella when they come into contact with the water in their water supply.