Quite a few orchids, if not most, benefit from a drop of 15 degrees or so between the day and night temperatures to induce spiking. Generally, 3 -4 weeks of dropped temperatures is what you are looking for.

For my Phals, I usually only let the temps go to 50 -55 degrees Farenheit. Keep in mind, that at this time with the lower temperatures, you will need good air circulation and usually to watch the watering--usually lower temperatures can also invite fungal infections (hence the air circulation caveat) and reduced water needs (ALWAYS ALWAYS CHECK before watering!).

Cymbidiums can take a more substantial drop in temperatures, 20 - 30 degrees in order to have them spike well. Dendrobium kingianum is another which will take a severe drop.

Not willing to take the risk of frost, or critters? Quite often, those of us living in areas which have less moderate temperatures (ie a definite fall and winter!) can just put the plants on or near a window sill.....the cold drafts and night temps from the glazing is enough to convince my phals that "It's cold outside! Time to make babies!" So snuggle your plants up to the glass and relax, you'll be doing the happy dance in a matter of months...