GRAND RAPIDS, MI - Thanks to its growing economy, West Michigan's housing market has shot up to No. 13 on a "hotness" index created by Realtor.com, jumping past some of California's perennially hot housing markets.

The jump from last month's ranking at No. 20 is because few houses are available for sale in Grand Rapids and don't stay on the market very long, according to Javier Vivas, an economist for Realtor.com.

The "hotness" index also is calculated by looking at economic growth statistics and the level of online searches for houses in a market, he said.

Unlike the California "hot" markets, West Michigan's housing market is attracting new homebuyers because housing is relatively affordable, Vivas said.

According to Realtor.com's statistics for May, homes in the Grand Rapids-Wyoming market were on the market for a median of 31 days. While that's down from April's calculation of 25 days, Vivas said more buyers have entered the market this spring.

As of Monday, the Grand Rapids Association of Realtors reported there were 1,385 single family homes on the market, down 20 percent from June 2016. Through April, the average price of a home sold in the Grand Rapids area was $207,105, a 9.3 percent increase over the previous year.

Other Michigan cities also popped up on the "hottest" list. Ann Arbor was listed at No. 15 while Detroit-Warren-Dearborn was listed as the 18^th "hottest" market on the list.

In Ann Arbor, houses were on the market for a median of 37 days while in Detroit-Warren-Dearborn, they were on the market for a median of 40 days. Fort Wayne, Ind.'s housing market was ranked 11^th, up from 14^th.

"This is officially the most competitive, fastest-moving spring housing market in decades. Some places like the Bay Area have become too hot to handle - and now a lack of inventory and affordability are allowing other markets to catch up," Vivas said in a news release.

While Realtor.com's list of the country's 20 hottest real estate markets in May still features nine from California, six of those have dropped at least two spots since April.

Nationally, in May, home prices were 10 percent higher than one year earlier.  Earlier this spring, the median list price for homes nationwide broke the $250,000 mark for the first time; now the median list price is $275,000 - a 10 percent increase over one year ago, Vivas said.