Does the soil feel very wet?

Was the smog very thick?

Does the pot have drain holes?

Do you plan to keep it in a container or plant in soil?

@Moiraine

Yes, I changed the soil and watered the tomato plant very slightly with the new soil. My tomato plant looks less droopy now, but it still looks droopy. I'm going to assume that it's stressed out at the moment.

Yes it was. It blanketed the entire sky.

@missingtheobvious

It looks like it has drainage holes.

It's a determinate tomato plant so I'm going to, hopefully, keep it in a bigger container later. If I don't have the space for the tomato plant, I'm probably going to the community garden to keep it there.

Hmmm... I think it was the smog then, if the soil wasn't too wet. The plant probably couldn't get to the CO2 it needed. If the smog is gone, it should fully recover.

Thanks :D