Roanoke hasn't hit 90 yet in the first 12 days of September, but likely will over the next 3 or 4 days, as dominant high pressure brings weather more akin to midsummer back to our region.
There is nothing unusual about a few 90-degree days in September -- Roanoke averages 4 each September, going back to 1912. There were only two such days in September 2020, but nine in 2019, the most since 10 in 2010. The last year with no 90+ days in September was 2009. The most was 16 in 1933.
Moisture will also be gradually increasing this week, making it more sticky after so many days of fairly low dew points lately since the passage of Hurricane Ida's remnants on the first day of the month, and also raising low temperatures to 60s to near 70. A few afternoon pop-up showers and storms can't be entirely ruled out in the first half of the week as high temperatures range from the mid 80s west of Roanoke to the lower 90s in the Roanoke Valley and lower elevations to the east and south. By late week, moisture will be thick enough with the potential for some passing disturbances on top of daytime heating into the 80s for more abundant showers and storms, though not likely a general rain.
The involvement of tropical systems -- Tropical Storm Nicholas in the western Gulf of Mexico, possibly another tropical disturbance off the southeast coast late week -- is not firmly established. High pressure appears likely to remain in control overall through this week and beyond, deflecting any cooler fall-like air masses away. So while it may not stay in the 90s for highs beyond a few days, sticky 80s days may continue for more than a week.