Yes, the heat and humidity can be brutal at the US Open. It's been averaging 85 degrees here this past week, and due to all the concrete buildings and asphalt streets which hold in all the heat, it can feel in the 90s. If it's really humid, and it usually is at the end of August, even if your parents are used to hot temperatures, the humidity can make them feel they are being steamed like a wilting piece of broccoli instead of baked.
There aren't a lot of places at the Open to stay out of the sun or rain. There aren't a lot of places to stand or sit in a shady spot. So we are talking 85 degrees in the sun or rain for HOURS. (Late August - September are usually when a hurricane is coming up the coastline. Expect some rain, bring umbrellas.) I have always felt the design of the grounds aren't built to be kind to elderly people or people with heat problems due to this. (I have always had problems with heat, so that makes me mindful of how hot it gets here. I also can't breathe well when it's really humid.) Have them invest in a couple neck fans or fans with misters. Make sure they are tested out to work and work well, before arriving. Also wear hats.
If your parents have a Chase bank credit card, tell them to bring it. There is a Chase Lounge building with air conditioning. But only Chase card members are let in via showing their Chase card. There is a practice court inside the Chase Lounge and they may get to see one of their favorite players practicing inside.
If they also have an American Express card, bring that too. There are perks for AMEX members. One is the coveted earphone to hear the commentators during the matches. If you go to the AMEX booth and they only give one earphone, even though there are two attending, not to worry, there is a second booth further down to nab another one. They will need to swipe the AMEX card again, but the swipers often don't work properly, so you will be able to get a second earphone.
I *think* a plain cheeseburger is about $12 now, which is usually the cheapest food item there. So, any other food entree is going to be way more.
The bathrooms with the least lines are
behind the food courts at Court 17.
Definitely get tickets to Arthur Ashe stadium no matter what day they go. Once they have Ashe tickets, they can go
anywhere in the venue, to any court, to see any match playing. They only have to line up to get seats to that match. All outer court seats are first come, first serve. NO reserved seating. If they don't have Arthur Ashe stadium tickets, they can go to any of the other courts, but not go inside Ashe Stadium.
In my opinion, if sun and heat gets to them, it would be better to get the evening match tickets which start at 5pm, instead of the morning session tickets. Although, if they do get the morning tickets, once they are booted out of the Ashe stadium for those with evening tickets, they can still
stay in the venue and go to any other matches playing, even during the evening. So, they can sit at the food court, have dinner, and go around and see more matches (just not in Ashe.) There is a huge Jumbotron screen in the food court area, to watch the match going on at Ashe. This is when it would be good to have those AMEX earphones.)
To be clear: Once they go out of the gates and leave the venue, if they have AM ticket, they will NOT be let back in after 5pm.
Yet they can stay inside all they way to 10pm-ish, when the last matches end if they do not leave. But, realistically, will they really stay all day? Or will the evening games be enough for them? Also, if it's the men's match they want to watch and the match goes to 3 sets, the game could end a lot later.
Depending on what the match ups are the #1 seeded players could actually be playing on one of the smaller courts. There were times that Serena Williams ended up on an outside court for a match while the males were playing in Ashe at the same time.
Your parents will know where a great match is playing, as once it is announced which court it will be on, several hundred people will move like a herd of buffaloes to that court. Again it is non-reserved seating, so if they don't move fast, they may not get good seats. However, if they already happen it be sitting in seats at that court, say, they are at the Louis Armstrong court, they do not have to leave. They just stay for that match.
Earlier in the week, there are more matches playing on all the courts. I think they are called "ground passes" are sold, with no access to Ashe stadium. As the Open gets to the quarter-finals, there are less matches over-all. Yet, they may get to see their favorite player in a doubles match on an outer court. There are also less attendees from the quarter-finals on. I think the "Ground passes" are no longer sold at that point as there are less matches going on. The whole venue is much more civilized as it's less crowded.