The heat is quickly fading from Miami's luxury housing market.

According to a new report from Douglas Elliman and Miller Samuel, the average sale price for luxury condos in Miami and Miami Beach plunged 30 percent year over year in the third quarter, to $948,700 and $2.6 million respectively.

The number of luxury condo sales also plunged, by 25 percent in Miami and 17 percent in Miami Beach.

The declines mark another step down for high-end real estate in the area, which had experienced a boom after the financial crisis. It comes as buyers from Latin America are slowing to a trickle and uncertainty around the presidential election is causing wealthy Americans to pull back.

At the same time, luxury buildings that were started during the boom years of 2013 and 2014 are now starting to come online, creating a glut of high-priced homes and condos.

Miami's results echo those from other cities in the U.S., where the highest priced real estate is faring the worst.

Luxury "is becoming a smaller part of the market due to the reduced emphasis at the top," said Miller Samuel's Jonathan Miller.

Inventory of luxury condos in Miami Beach jumped 30 percent in the quarter compared with a year ago, to 1,235. These properties are now sitting on the market for an average 126 days, more than double last year's number.

In broader Miami, inventory rose 11 percent, resulting in a 40-month supply of luxury condos. Inventories for single-family homes in both areas are also higher.

Given these broad-based increases, Miller said the luxury real estate market in Miami is likely to get worse before it gets better.

"In terms of the luxury market, more product is coming online as developers try to reconfigure them to meet the demand of a changed market when they hit the market," Miller said. "The excess supply of luxury product will likely rise over the next year. "