When is it to hot to cut the grass?

Never.

110 degrees in Phoenix is not the same as 90 degrees in Jersey. Leave your grass alone until the temp drops below 85 and drink a lot of water. The humidity level in the Northeast is not something to take lightly.

PLOW it, PAVE it and PAINT it green!

I lived in No NJ for 10 years and my hatred for cutting the grass was legendary, followed closely by my hatred for raking leaves which then had to be bagged and transported to a mulch center. Given that the teenagers in No NJ stopped cutting lawns for pay 35 years ago, HIRE a service and ditch the lawn mower. Money should not be an obstacle, given the type of green you need to pay for a house and taxes in that part of the state. Unless of course, you enjoy trucking ye olde Craftsman to Paramus for Sears to maintain.

Rich

I'm retired but I have a lawn business to keep me busy. When it is hot, the grass does better to be left at least 3" high. It keeps it moist and helps it stay healthy. With the high heat, water the grass often. Cut, no more that 1/3" the length and make sure that the mowers blades are sharp. Cut in the late PM when it's cooler. You cover your head, wear a dust mask if dusty and keep hydrated just like the grass. I cut grass all summer and the dust/dirt is more trouble than the heat.