The weather has certainly taken a turn for the worse in recent days. However the red-tails and other birds are well equipped to handle it. The parents brood the eggs to keep them warm and protect them from the elements. The eggs are typically maintained at between 98 and 100 degrees. You may notice an area on the mother's belly where the feathers look more sparse---many birds develop a "brood patch" which is an area where the bird looses some of its feathers toward the end of the egg laying period. This area also develops additional blood vessels to bring warm blood closer to the skins surface. This is the area of her body that she keeps in close contact with the eggs when she is lying on them.
It is also okay for the parents to be off the eggs for limited periods. Eggs can survive a substantial amount of cooling. Cooling tends to slow down development but not cause harm unless it is prolonged.Eggs are much more vulnerable to heating--just a few degrees above normal can be lethal to the eggs.
Several years ago we had to remove peregrine falcon eggs from the Interstate Bridge after the parent was hit by a car. We don't usually "rescue" eggs, but peregrines were at the time still an endangered species. The eggs were actually exposed to a cold driving rain and temperatures in the 40's for more than 5 hours. The only way to get to the top of the bridge at the time was to ride the lift span up and down because the access stairs were under construction. In order to lift the span, the bridge tenders had to stop traffic....at rush hour no less. I remember standing at the top of the bridge with the wind and rain howling in my face hugging a box containing the eggs inside my jacket while we waited to get lowered back down thinking that there was not hope that the eggs would hatch. None the less when we returned to Audubon we stuck them in an incubator and a few weeks later we had three healthy peregrine chicks!
The feathers that folks are noticing in the nest are not from the mother---they are remains from the pigeon that she has been consuming over the past couple of days.