I'm a rising senior in university in Canada, and currently doing a semester abroad in Singapore.

Sometimes a property will remain vacant because of market timing - like being mid-semester in a college town, or in the winter when the weather is challenging. 

You can get short term rentals during those months and the rates are BETTER than semester rates,

So I am in my last semester of completing a general associates degree.

They were coming into town this month for an event at the local college, and that college unfortunately closed for the rest of the semester.

I have a SF student rental that just moved their spring semester classes online due to the Coronavirus, I have a few tenants threatening to move back home but the lease they signed runs through July 2020, yes I feel terrible about the situation but they need to abide by the lease they signed..thoughts?

Perhaps there will be another wave of the virus in the fall, but if you've got adequate protections and a backup plan in place, like that 12-month lease Roni mentioned, and you get some tenants in place between now and the next semester, barring any other issues that might arise in the normal course of business, you'll ride this wave with the rest of the student rental community and along with all other investors in your region.

Unit 2 is empty which is weird being in the middle of a semester.

I have about 10% student rentals, of which, 3 jumped ship early and moved out right after the university went to on-line only for the remainder of the semester. 

If they havent closed for the whole year already they could still be required to finish the semester so where is he going to stay?