You say "bottles" - that's the good news. You have a definitive answer to your question in your possession. Pull a cork.
A summer stored at temperatures near 100F could easily have ruined this wine. Porto due to its alcohol content is sturdier than table wine, but conditions as this could have cooked it.
Before you pull the cork, inspect all your bottles. Look for protruding corks, even a millimeter. If the capsules are 'wax', see if they are cracked. Look for trails of seeped wine on the neck or labels of the bottle. All are indications that the wine cooked, expanded with the heat.
Now that I have said all that, I admit I just now remember you said "tawny and ruby". Whole different animal. These wines are vintage dated? Very unusual for tawny or ruby ports.
Tawny and ruby ports are bottled for immediate drinking. They are not "constructed", that is to say vinified, in such a way as to require or benefit from additional aging. IMO opinion, these wines would be in worse condition today than in 1989, whether or not they went the the OKLA summer or not.
Here's what you do:
Buy a bottle of Delaforce 10 year old tawny. It'll cost you $20. Pull the cork. Now you can find out what this wine should look, smell and taste like.
Now pull a cork of one of your stored bottles. Look for unpleasant smells or smells of cooking sherry. Look for a lot of sediment (tawny or ruby portos should show no sediment) I would not be surprised if these wines were shot.
If the wines are good now, drink them up. No need to hold them 5 years; only chancing them going bad.