is 40 hours Part Time?

So I work at a construction site-when I was hired on I was working 58 hours a week! that was exhausting. Then after about 2 months it got cut down to 48. That was more tolerable. Now this morning I was informed that it will be going down to 40 hours! While that is nice, and I will have a 3 day weekend-how will we pay the bills? It will feel like I am never working. This will be through Labor Day but may change sooner. I know that after that we will be swamped with work-the department I am in is Start Up and we have to wait for Construction to finish, so there is a huge amount of construction going on-they are doing 58 hours a week right now and when that is finished up, it all gets turned over to us! But I couldn't ask for a better time to be on 40 hours-this summer will be fun! :)