Of the sales contracts signed in May, according to numbers compiled by California-based analyst Mark Hanson, 31% were for completed homes, so buyers likely would have locked in their mortgage rates near record lows. Those deals would close easily. And 24% were for homes under construction. Some buyers may have locked in a rate if the home was almost done, but some likely did not.

The biggest risk is with the rest of the contracts. Of the signed contracts in May, 36% were for homes that were not yet started. Completion and closing would be anywhere from three to nine months out. Those buyers, in most cases, could not lock in mortgage rates yet. Rates are up a full percentage point from the beginning of May and continue to rise, writes CNBC.