How can I work on changes to my Wordpress site on my computer -- not internet?

Hi - My Internet just went down at my house, and I have a deadline coming up. I won't have a technician here for a few days. Is there any way that I can download my Wordpress site and work offline on my computer, and then upload changes once I'm back online at home? A plugin maybe?
I'm at Starbucks right now, but I don't think they are open as late as I need them to be.