I live in the midwest - zone 5 - and got a few lemons last year from my (new) lemon tree, actually more of a bush. Now it has over a dozen blooms, little to mod. sized green buds. It did beautifully out on my sunny deck over the summer but now that it's cold, it's in my kitchen (large windows - lots of sun). Do I need to keep it at a certain temperature throughout the winter months to preserve the buds so they keep maturing?
I've found that average home temperatures work just fine. Avoid drafts and keep slightly moist (just don't let it get too dry). Pay attention to the possibility of spider mites in the drier indoor air.