As Heat Wave Intensifies, How to Prepare for a Power Outage Be prepared the next time you lose electricity with these handy alternative power sources.

Scorching heat. Oppressive humidity. This is the forecast for most parts of the Northeast and Midwest U.S. this week. For the next few days, temperatures are expected to be in the 90s, and the heat index could reach 100 degrees or higher, according to the National Weather Service.

In these sauna-like conditions, the power grid in these regions will likely be put to the test, as fans and air conditioners in homes and offices will undoubtedly be turned up full blast. If power sources fail, it could spell bad news for busy entrepreneurs. Nothing's worse than being stranded in the dark with no electricity to keep your smartphones, tablets and other devices powered up and productive.

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While far from an exhaustive list of options, here are a few tools that can help keep your devices going and keep you productive for a few extra hours during any type of power-zapping situation:

1. A back-up power source: When the lights go out, rely on a back-up power source to keep your devices on. One way to go is to carry (and keep charged) a portable battery, such as a myCharge universal power pack from RFA Brands. Starting at about $50, these extended batteries can recharge Apple and Android smartphones and tablets.

If you're looking to charge multiple devices, one option is the Powerbag, a backpack that includes a built-in battery that can charge up to four mobile gadgets and laptops. Backpack designs start at $140. Briefcases start at $150. Battery size and charge capability vary.

2. A mobile hotspot: If your power goes out and your internet connectivity goes along with it, try using a mobile hotspot to get your devices back online. Turn it on and connect to it like any other Wi-Fi network.

While many smartphones have hotspot capabilities built in, you can purchase a hotspot device from cellular carriers such as Verizon and AT&T. For instance, Verizon's "Jetpack" line of hotspots can allow you to connect up to 10 Wi-Fi-enabled devices on its 4G LTE network. The 890L model starts at $19.99 with a two-year service contract.

3. Self-generated power: There's not much you can do when you've been without power so long that all your back-up battery power is gone. When that happens, consider using gadgets that run on energy you can generate yourself.

One example is a hand-crank powered flashlight with radio and USB charging port from ER Emergency Ready. For about $35, this handy tool comes with a LED bulb for emergency light, a radio that picks up AM, FM and all 7 NOAA Weather Band Radio Alertchannels, and a universal USB for charging a mobile phone so you can make short calls or send text messages. You turn the crank and it generates energy for an internal battery.

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This is an update of a piece that ran previously.