I have done that – put my tent directly over me when it started raining.  For a few hours there wasn’t a lot of condensation. All night there would be a lot of condensation.
Another thing I’ll do is stake one side of the tent and fold it over itself to my side. Then, if it starts raining I can quickly erect the tent.
Or, if there’s only a small chance of rain I’ll just leave the tent and pole ready. And rain jacket. Then, when it starts raining, I can quickly throw the tent over my sleeping bag, then erect it, then go back to sleep.



