While the rest of the country is in a good position to avoid a housing bubble for the next five years, a new report from Zillow says San Francisco may already be in one.

The site found some of the experts polled believed San Francisco and New York were already in a bubble, while Boston, Los Angeles and Miami may be at risk in the next three years. A third of those polled said San Francisco was in a bubble where home prices have reached unsustainable levels for the local market.

President emeritus of the American Real Estate Society Grant Thrall questioned whether the international buyers and REITs that have driven up prices will hold onto those homes.

Zillow chief economist Svenja Gudell says a handful of markets, and especially the Bay Area, are very hot and it's possible home values may fall in those places as residents are priced out, particularly when interest rates rise.

Fed Chairman Janet Yellen has said she plans to raise interest rates this month, barring an economic downturn.