On the meteorological calendar, fall began over a week ago. But some of the hottest weather of 2013 surges into the region midweek.

A strong area of upper level high pressure, or heat dome, is building in the central U.S. It will steadily march eastward, with its core over the Mid-Atlantic late Tuesday into Wednesday.

Migration of upper level high pressure system between today and Thursday from GFS model (WeatherBell.com)

Already, the scorching airmass has set records.

Wichita, Kan. and North Platte, Neb. soared to 101 Sunday, record highs for the date.

While yesterday the Plains simmered, today the Midwest gets baked.

The Minneapolis Star Tribune’s Paul Douglas says it could be the Twin Cities’ hottest day of the year with mid-to-high 90s expected.

(Douglas notes this stunner: Minneapolis has had more 90+ days this summer (18) than Atlanta (17)).

Chicago is also expecting at least mid-90s today and perhaps Tuesday as well.

“If the mercury reaches 95 degrees Tuesday, it will not only tie the day’s high temperature record set in 1983 but will be the city’s hottest reading this late in the season since a pair of 95-degree highs that year on September 9-10,” writes meteorologist Steve Kahn on the ChicagoWeatherCenter blog.

Weather.com says Des Moines could hit 100 today, which would be its latest 100-degree day on record (dating back to 1878).

Here in Washington, high Tuesday climb to near 90 but it’s Wednesday when models simulate the heat’s climax. Low 90s for highs are close to a given, with mid- to even high 90s a possibility.

This NAM model simulation indicates highs of 94-97 in the D.C. metro region.

NAM model simulates very hot temperatures Wednesday (WeatherBell.com)

The hottest day of 2013 so far has been 97 (from July 17). How ironic it would be for us to best that mark, in September?

In order for Wednesday’s heat to be record-breaking, we’ll need the temperature to reach 98 (from 1983). I’d give that one-in-four odds.

It will also be humid Wednesday (dew points 67-70), which will make it feel like 100 in the afternoon.

This will not be a protracted heat wave. Although Thursday is on the toasty warm side, we’re back into the 70s Friday through next weekend.