Oahu’s housing market had a breakout month in April with a spike in sales despite inventory that remains relatively constrained.

The number of previously owned single-family homes sold surged 22 percent to 301 in April from 247 in the same month last year, according to data released for publication Thursday by the Honolulu Board of Realtors.

"The Honolulu real estate market really heated up in April," Jack Legal, board president and owner of Legal Realty in Kapolei, said in a statement.

Big monthly swings up or down in sale volume have happened occasionally in the last several years. The two previous changes that were bigger than last month’s were a 24 percent drop in November and a 25 percent gain in August 2013.

Other aspects of the market in April — condominium sale volume and median prices for condos and single-family houses — achieved modest gains.

The median sale price for single-family houses rose 4 percent to $674,900 last month from $648,000 a year earlier.

The median condo sale price also rose 4 percent to $370,475 from $355,000.

Condo sale volume edged up 2 percent to 454 from 445.

For the first four months of the year, sale volume and median prices remain in a modest range of movement for both single-family houses and condos.

The year-to-date total for single-family home sales is up 3 percent to 956 from 929 a year earlier, while the median price is up 4 percent to $675,000 from $650,000. Condo volume is down less than 1 percent at 1,433 from 1,438 in the same period, while the median price is up 6 percent to $365,500 from $345,000.

Legal said demand continues to outpace supply, though he noted that inventory of homes on the market is "slowly improving."

The improvement has been more pronounced for condos, which had three consecutive months of rising inventory.

Last month there were 1,902 condos on the market, which was up from 1,630 in January and is the most for any month since August 2011. The higher inventory last month was partly the result of significantly more listings added in March along with fewer sales in March.

Single-family house inventory last month totaled 1,244. That was up from 1,077 in January, though inventory was higher during a few months last year.

Higher inventory has the potential to result in more sales in the coming months if demand remains strong, given that homes sold in April reflect purchase contracts typically signed one to three months prior.

Low interest rates, rising personal income and job growth are largely driving homebuyer demand while higher prices and still relatively low inventory are keeping somewhat of a damper on sales, according to local economists.

A University of Hawaii Economic Research Organization report released in March called home prices to date "mild" considering the volume of homes on the market, and projected single-digit gains in median price this year and in the next two years.

UHERO projects that Oahu’s median single-family house sale price will rise 5 percent to $709,600 this year from last year’s record $675,000 and then rise 9 percent to $772,200 in 2016 and 6 percent to $816,800 in 2017.

For condos, UHERO expects the median price to rise 4 percent this year to $365,000 from last year’s record $350,000, and then rise 8 percent to $394,700 in 2016 and 8.4 percent to $428,000 in 2017.