I haven't heard of any yet, but they happen every time heat this intense happens.
I've never been affected by any brown out since I've bought my house and setup my tank but just a reminder to people that have generators to start them up and make sure they are working.
If you don't have one you should think about buying one. I know they are pricey, but think about how much you have invested in your fish tank and food in the fridge/freezer and then the ability to watch TV and run a fan. If you go with a bigger one, you could also run the A/C (4000+ watts). A cheap 1000-2000 watt can be had for under $200.
To figure out the wattage needed, just multiply the amperage X voltage.
For example.... My metal halide ballasts are 5A's each. So 5a X 120v = 600W MAXIMUM. They MAY need a that much but when they are running it is much lower - Its when they turn on is when they pull the most. I actually hooked up a watt meter to them and they never pulled more than 190W's,~1.75 Amps.