I have mine near a window all winter long. Don't let the plant touch the glass. Don't allow any drafts, keep the window shut and locked and check for drafts (a killer of plants). Orchids thrive on a temperature drop to promote new growth, so don't worry. Well, the ones that you have do. Phals do not want too much light. If the sun is pouring in and your leaves are directly in the sun...not good. If the leaves feel warm, move them inward away from direct light. Oncidiums seem to like the light more. Temps for me inside can drop to 57 degrees in winter (I live in Maine). Drafts are the enemy, though. Watch out for them. Keep a fan going in the area for air flow. Shouldn't be directly on them, though.
Orchids are pretty resillient, so don't worry so much. If you look in my gallery, you will see my sunroom plus other windows with phals and other type orchids and you will see drifts of snow on the other side. So don't panic, they will make it!