Temperatures compared to normal on Wednesday per the European weather model. (Weatherbell)

Washington’s final burst of heat in 2019 is set to put an exclamation point on a historically hot summer, which has bled into fall.

Some spots could come close to 90 Tuesday, but it is Wednesday when temperatures really spike. There is some chance Washington’s highest temperature ever recorded in October — 96 degrees, set in 1941 — is threatened. Unseasonably hot weather could even linger into Thursday.

Hitting 90 degrees once in October is somewhat rare, as we average only one such occurrence every four years or so. In an average year, our last 90-degree day is Sept. 11.

But this year, we’ve posted eight 90-degree days since Sept. 11 and seem destined to tack on at least one more.

Wednesday-forecast highs from the National Weather Service as of Tuesday morning.

On Wednesday, 90 degrees or higher is almost assured, and all the local record highs for Oct. 2 are likely to fall. They are:

  • Washington: 89 degrees (last set in 1986)
  • Dulles: 89 degree (1986)
  • Baltimore: 89 degrees (1986)

Most models project highs in the low- to mid-90s Wednesday, flirting with that 1941 monthly record of 96.

Although it’s increasingly uncertain that Thursday will also be super hot, thanks to a cold front headed this way from the northeast, here are the records for Oct. 3:

  • Washington: 92 degrees (1879)
  • Dulles: 86 degrees (2018)
  • Baltimore: 92 degrees (1919)

Thursday 2 p.m. temperatures from the NAM weather model show a front in the region that could mean it's cooler or hotter than shown.

If and when the record high is set Wednesday, it will be the fourth record high in Washington since August. That’s the most record highs during the warm-season months of April to October since five were set in 2016.

The other record highs this summer came Sept. 12, when it hit 98 degrees; Sept. 5, when it was 96 degrees; and Aug. 19, when a high of 98 degrees tied the record.

Should 2019 join the list of years with October 90s, it will be part of an elite club. Eighteen years out of the past 147 have seen at least one day at or above 90 degrees during the month, and five have seen two or more. The most 90s on record in October is five in 1941.

The most recent 90-degree day during the month came just last year. On Oct. 4, 2018, it reached 90 degrees on the nose. Before that, we need to go back to 2013, when there were two such days.

Hottest October days.

The last time we had a heat wave in October, defined as three days in a row with highs at or above 90, occurred in 2007, from Oct. 7 to 9. The peak temperature in that run was 94 degrees. The city almost pulled one off in 2013, when it was 90 degrees, 89 degrees and 91 degrees from Oct. 4 to 6.

Before that, we need to go back to 1941 for another October heat wave, and it was a biggie. It ran four days (there were five total 90-degree days that month) and peaked at 96 degrees, which is the record for the month, on Oct. 5.

Although a bit painful for so late, it would seem fitting to pick up more 90s in October, given this particular year.

90-degree days through the end of September. (Ian Livingston/The Washington Post)

The 61 days at or above the 90-degree mark through Monday stands in third place for the most on record. While the record of 67 such days in 1980 and 2010 is safe, this year will be remembered for its relentless barrage of toasty days.

These days threatening to reach and pass 90 degrees are almost certainly the last until 2020. The outlook for Friday and beyond looks a whole lot more like fall, even if we think October ends up warmer than normal on balance.

An error in the hottest October days chart was corrected after publish.