Don't think I ever got any "heavy rain" here, just non-stop light rain. Appears to be about two inches at my place so far, which is in keeping with the original forecast. Looking at the radar now, it seems to be finally moving out.
I have a second monitor but it was extended and not mirrored. So I was able to blindly put in my password and drag items from the Apple monitor to the second monitor. I caught the Hard Disk and was able to open System Preferences and mirror the two allowing me access to my stuff. My iMac is called "Vintage" by Apple since it is a late 2012 model. Apple will only fix it if parts are available and the Apple person I talked with said they can't fix it. I would have to go to a repair shop if my part was even available. Once an Apple computer has been discontinued for 7 years it is considered "Obsolete" and parts are no longer available.
The computer I want to buy is $2900 so at this point I am just going to buy another external monitor and sit my computer on the floor and run with two external monitors if my computer can handle that. I will wait a while before spending $2900.
That is about what I spent for my new Mini with 6-core i7, 64gb RAM and 2tb SSD, plus a 32" BenQ screen. I also considered an iMac but wanted a bigger and more adjustable screen, plus I was concerned about the same issue you are having... if something goes wrong with the computer and it's not worth fixing, you basically just throw away the expensive screen.
It is a lot of money and I agonized over it for awhile. Would have been cheaper to use my own RAM, but there are issues with that. I was also upgrading from a 2012 Mini and 2013 MacBook Air. IMO, 8 years is a ripe old age for a computer if you have anything more than casual needs...
But you should be fine with the external screens on the iMac in the meantime, I'd think.
Flood Watch National Weather Service Mount Holly NJ
310 PM EDT Wed Oct 28 2020
...FLOOD WATCH IN EFFECT FROM THURSDAY MORNING THROUGH THURSDAY
The National Weather Service in Mount Holly has issued a
* Flood Watch for Delaware, northeast Maryland, South Jersey, and
far southeastern Pennsylvania.
* From Thursday morning through Thursday evening
* The remnants of Zeta will be moving through our region, bringing
a few waves of heavy rain from Thursday morning through Thursday
evening. Storm total rain of 2 to 4 inches is possible across
the watch area. This could lead to overland and road flooding as well as small stream flooding.