When to bring the geraniums indoors?

I want to try to save the geraniums this year. 3 in pots are still blooming and I have 5 more in the ground. Those have some flowers too.
The temparature drops down to low 40s here at night these days.Should I keep them out longer or bring them in already?

 

I'd bring them in!

 

I dug up my favorites and have moved them in. I'm sad to say that I couldn't save them all~ not enough room but the few I managed to save will brighten my office this winter