Manhattan real estate prices are heating up to record high, and they probably won't go down anytime soon.

The CityRealty monthly report released Tuesday said the average price for a Manhattan apartment in May was $1.9 million -- the highest in their records -- and 876 sales took place that month.

The report, which analyzed housing data from several city agencies, found that May sales totaled $1.7 billion, which is higher than the GDPs of nearly 20 countries, CityRealty noted.

In April, the average price was $1.8 million and there were 880 recorded sales.

Gabby Warshawer, a spokeswoman for the real estate listings site, said the trend will continue into the season.

"Prices are definitely going to go up this summer," she said. "It's a combination of high-priced inventory and a lack of resale."

In May there were 367 condo sales in Manhattan, which had an average price of $2.5 million, and 509 co-op sales, which had an average price of $1.4 million, according to the report.

Warshawer said new units hitting the market come with big price tags and homeowners haven't been selling much lately.

"Sales volume is down, so fewer apartments are trading," she said. "Sellers want to get the highest dollar they can so they will wait."

The biggest recorded Manhattan sale was a 12th-floor condo at the New Museum Building in SoHo, according to CityRealty. The five-bedroom, five-bathroom, 7,837-square-foot apartment sold for $34 million.

Downtown Manhattan led the borough in May sales, accounting for 35% of the total purchases in the borough that month, the report said. Midtown, which has several new developments -- One57 on West 57th Street, for example -- accounted for 24% of May sales.

Despite the numbers, Warshawer noted that it's not impossible to find a bargain in Manhattan this summer if buyers are calculated and keep an eye on listings.

"It pays in New York to be an educated consumer," she said.