I’ve experimented with the old style of window fans (two small circular side by side fans) as well as propping a box fan in our windows.  This unit far surpasses the performance of these other options.  This is quiet, sleek, does not let in much light (so great for baby and toddler rooms that wake up at the first sign of daylight), and is perfect for double hung windows. 
I purchased two for two separate bedrooms and am considering a third after experiencing how awesome these are.  
Only change that I would make would be have the speed level lights dim once you’ve made your selection (they are kinda bright at night and I had to cover them). 
No issues with rain coming in either.   

Buy one.  You won’t be sorry.  You’ll sleep better and keep from running your AC so much on those “on the fence” temp kinda days.