| In California, you have no other way of saving over your geraniums since you would have no way of keeping said plants in a "cool" room. Yes, but I suggest you keep them flowering only as much as the light will extend their time. The sun's intensity is almost now at its lowest ebb....December 21st...the winter solstace...and thereafter, the sun begins its long road back to June 21st...the longest day of the year. Soon your plants will lose their vigor. When this happens, remove any bloom, cut back the plant by 1/3....1/2...however you see the need.
Give them a clean pot, fresh potting soil/mix, (have something between the soil and drainage holes) and water only as the plant requires it after letting it dry down between.
Don't fertilize until new growth is evident. That wont happen until about mid February when the sun begins to give sufficient energy to promote new growth.
Then only feed according to the plant's size and growth rate. You can pretty well put it as close to the window at this time as you can...just don't let it touch cold window glass.
Hopefully, you can keep it going until your usual time of planting out. That's pretty soon isn't it..in California. The February date mentioned is for those of us that experience winter....and snow....lots of snow...lots coming this weekend.
In your neck of the woods or where the traffic is never-ending...just kidding....you should be able to keep your plants going for another couple months anyway.
Just cut it back when they lose their vigor. | 
