How soon can I overseed this fall in Alexandria, Va and what are the risks?

[newbury]

I'm in Alexandria, Va trying to do a lawn renovation. Putting down a mix of tall Fescue on a sunny lawn.

Lawn was old and had about 10% or less weeds.

I limed last year
I put down crabgrass preventer, fertilizer in the spring.
I've tested the soil, pH is fine, nitrogen is low, K is OK
I killed the weeds by the end of August.
I put down a layer of 22-0-5 last week.
The lawn gets very little traffic and is not compacted at all so I decided not to "aerate" it but did dethatch. And got all the thatch off with a mower and bagger.
It's now mowed LOW and getting plenty of water.
I plan on fertilizing a few more times.

Historically high temps average below 80F starting next week. In reality every day is showing 80 and above for 10 days.

I need to get my butt to Mississippi for a month or two around mid-October and don't have anyone I can trust to water the lawn while I'm gone.

How much of a hit should I expect to take in germination problems due to the heat?

Normally I'd let the temps get down to the mid-70's but the trip to Mississippi has to be done and I'd really like the lawn to be almost mowable by the time I leave.

Thanks for any advice.

 

[Streetcar]

If you can water the area, you can plant now.if you can't water the area seed over winter
On side note, if your existing lawn is fescue, there is no need to dethatch the lawn. Thatch does not form in fescue

 

[newbury]

If you can water the area, you can plant now.if you can't water the area seed over winter
On side note, if your existing lawn is fescue, there is no need to dethatch the lawn. Thatch does not form in fescue

Thanks.
I've only been here since 1984 and my usual routine was once every several years (3 to 5) I'd mow low once in the fall and throw down some tall fescue mix. This is the first time I used a dethatcher.

My normal mowing method is "mulch in place", I've always relied on a little fertilizer and time to decay the mulch over the winter. I actually had to borrow my son's mower w/ bagger because I don't have one. But I wanted to see bare ground on which to put the seed.

The "thatch", or whatever you want to call it, was a 1/2" thick dense layer of dried dead grass cuttings. I would not have expected grass seed to germinate well on top of that layer. In the past I observed that sometimes it germinated, sometimes not, but seed was cheap. Water ran through the thatch like it was a metal sieve. Now, after dethatching and low mowing/bagging there is mostly bare ground between the clumps of grass.

I'll probably seed Thursday or Friday after a potential 95 degree day on Wednesday.