|There's not any reason to use a light meter outside, unless you're shooting with strobes.
A light meter is used primarily for studio situations where strobes are being used. The reason is, there's no way to make your camera fire the strobes and meter while the strobes are on, so you're not able to determine the exposure with just your camera. You can use a meter to fire your strobes and get a reading while they're on. You set up your camera exposure in manual mode using those readings.
In the age of digital film, it's not absolutely necessary to use a meter at all. You can guess at the exposure, take a shot or two, adjust based on the results, repeat. But if you've gone so far as to spend money on strobes, you probably find the cost of a meter money well spent.