A new real estate “Hotness Index” is loaded with Bay Area housing markets, which is only to be expected.

Less expected is this: the Vallejo-Fairfield market in Solano County is the No. 1 “hottest” in the nation. Vallejo, a city whose reputation has been tarnished through the years by news reports about crime and gangs, has established itself as a hot housing destination, according to the June index from Realtor.com.

Last month’s sale price for a single-family home in Vallejo was $365,000 and properties are moving quickly.

“Something’s on the market, and you look at the map and see we’re about the cheapest place in the Bay, with a fast commute to the city,” said Ron Gold, a Vallejo-based agent with the Re/Max Gold real estate franchise. “If you want something cheaper, you’d have to go to Stockton.”

People are going there, too. The index ranks the Stockton-Lodi area as the 14th hottest market in the U.S.

The monthly index measures where houses are selling the fastest — they’re typically gone within 31 days in Vallejo-Fairfield — as well as which markets are generating the most listing views on realtor.com.

Beyond that, the index has become a reflection of the Bay Area’s housing crisis, which is pushing commuters to purchase homes at relatively affordable prices in out-of-the-way places.

Yes, the San Francisco-Oakland-Hayward metropolitan area is the No. 2 “hottest” in the country, and San Jose-Sunnyvale-Santa Clara is No. 9 on the list.

But then there is the Sacramento-Roseville-Arden-Arcade metro area (No. 4) and Santa Rosa (No. 17). Yuba City – in Sutter County, about 40 miles north of Sacramento — is the nation’s 19th hottest market, and Modesto is No. 20.

Realtor.com reports that “there were 11 percent fewer homes on the market (nationally) in June 2017 than during the same time last year, marking 24 consecutive months of year-over-year inventory declines.”

Javier Vivas, Realtor.com’s manager of economic research, added that “more markets than ever are struggling with inventory problems; in 80 percent of markets there are fewer homes for sale currently than this time last year.”

Given that the housing supply is at historically low levels in much of the Bay Area — where the job force keeps growing along with buyers’ demands for homes — it isn’t so surprising that the march of gentrification is reaching Vallejo, Stockton and Yuba City.

“We always make the 10 o’clock news for some reason, going back to the 1980s,” said Gold, the agent in Vallejo, “but we’re not really a whole lot different from other communities.”

In 1998, he bought his own house for $125,000: a modest place, just 1,300 square feet. He since has more than doubled its size, turning it into a custom home with granite counters and a three-car garage. He figures it’s now worth between $600,000 and $700,000.

About 25 miles to the south, Pacific Union agent Carla Buffington has watched as more and more upscale homeowners move to West Oakland and the Berkeley Flats, both previously deemed affordable, though not so much anymore.

“There’s just a lot of crazy sales, ” she said. “You just go, `Oh my gosh. Who pays that for that?’”

This year in the Flats, she said, four homes have sold for more than $1 million.

“They’re these transitioning areas and they’re close to the city,” she said. “You can fly over the Bay Bridge, and people are looking at it and saying, `Well, I can afford a lot more here than I can in the city.’ If you have a million dollars and you can’t get a three-bed, two-bath in what’s considered a little bit nicer neighborhood, you get pushed.”