be upon (one)

1. To be one's responsibility or obligation. It will be upon our PR team to come up with an exciting way to advertise this product. The obligation to provide evidence is upon the prosecution. I know he doesn't want to part with this old camera, so, if you really want it, it's upon you to convince him.

2. To be forced or imposed on one, as of some catastrophe. If the two countries don't stop this antagonistic back-and-forth, nuclear war could be upon us! A plague has been upon the region for several years. Millions have died. We need to get out of here—the hurricane will be upon this area by nightfall.

3. To be looming or have recently begun. Let's meet soon—once the back-to-school rush is upon us, we won't have any free time. Even though I know winter is upon us, I still can't believe it got so cold so fast! Get ready for a lot of family drama now that the holiday season is upon us!

be upon

To be imminent or just beginning to have an effect on someone or something: Winter is upon us, so we'd better be ready to shovel lots of snow.