An ideal area to proof your bread would be between 75-85 degrees, with some humidity. The steaming pan of water will create that humidity. I know some people who will turn their ovens on then off, to proof their bread in the retaining heat. My only concern would be the lack of control with the temperature. Yeast will die at 140 degrees, and it would be very easy to allow the oven to get too warm before putting your bread in to proof. Some of my bread-baking friends will use the warmth of their oven light or pilot light to aid in proofing. I prefer just to let my dough rise in a warm area of the house - near a heater, the dryer, a sunny windowsill. I feel like I have more control over the process, and a better gauge of the environment. But, if oven-proofing has worked for you in the past, I would stick with that method.

A warm oven is a great place to rise dough. The oven light, depending on the amount of heat it gives off, is a good way to give the oven some heat. In Germany, most professional artisan bakeries proof at about 30°C (100°F). To use your oven as a proofer, place a thermometer in the oven, turn the oven on to the lowest temperature on the temperature control knob/button for a few minutes and watch the thermometer temperature rise. As the oven warms up close to 100°F turn the oven off. Watch to see that the temperature is not too hot before putting the dough in the oven. If your bowl of dough is sealed with a lid or plastic wrap, the boiling water won't make a difference. However, if the bowl is sealed, it will retain the moisture in the dough and the sealed bowl will provide a nice and humid environment for the dough.