U.S. house prices rose ever so slightly in the third quarter over the second quarter, according to the Federal Housing Finance Agency’s seasonally adjusted purchase-only house price index. The HPI, calculated using home sales price information from mortgages purchased by Fannie Mae and Freddie Mac, grew 0.2% on a seasonally adjusted basis in the third quarter from the second quarter. On an unadjusted basis, prices rose 0.75% during the period. However, seasonally adjusted home prices fell 3.7% in the third quarter of 2011 from the same period a year earlier. (Click on chart to expand.) FHFA’s seasonally adjusted monthly index for September was up 0.9% from its August value. On an adjusted basis, prices grew 0.7% during the month-to-month period. “In most regions of the country, third-quarter home values were relatively stable, even in some areas that experienced sharp price declines in preceding quarters,” said FHFA Principal Economist Andrew Leventis. “While most housing markets still face stiff headwinds, the fact that some beleaguered states — such as Idaho, Florida and Utah — saw quarterly price increases is a positive development,” Leventis said. FHFA’s all-transactions house price index, which includes data from mortgages used for both home purchases and refinancings, increased 0.9% in the third quarter, but is down 4.3% annually. Write to Justin T. Hilley. Follow him on Twitter @JustinHilley.