Hey there folks, as roofing contractors we roof every day, it's our craft and we are proud of our work. Weather is always a consideration but for some reason home owners tend to want to inform us on the current weather situation. As if we haven't been at Mother Nature's mercy for the past 22yrs. Please if you trust us enough to hire us just know that we will truly know more about the weather situation than you could ever imagine. If your roof leaks on our watch we have failed. It's our main goal as roofers to keep your home watertight. If you want to be helpful, there are many other things one can do as the home owner. Like getting us some water, or minimizing distractions and going back inside:) Most roofers will bring all manor of tarps and underlayment to get your roof dried in as fast as humanly possible. Your typical exposed time frame is hardly ever more than 1hr. Once the underlayment is on, you are watertight. With the advent of these high quality synthetic underlayments it makes it really easy to cover up overnight. So no, the roof doesn't need to be completely done to be watertight. So if a homeowner wants to feel good about their choice in installer there are three basic things to check. 1) references, 2) insurance and 3) that your hiring the guy that is actually selling your roof. What I mean by that is don't have them send a subcontractor crew in. This usually means all the things the seller and the homeowner agreed on fly right out the window. The subs just want to get done fast at all costs. I tell my clients, "I sell it, I do it". Hope this helps someone..