The weather governs my camera and it should govern yours too, if you're serious about any sort of photography outdoors. Weather and photography literally go hand and hand. It determines your camera settings, the type of lightning for your shots, and scene you'll be photographing.
Weather as a subject means it is the focus of your photo. The reason for snapping the shutter. For example, when I set out to take lightning photos I pay close attention to the weather (obviously) even days in advance. The chance of storms, development, and movement of storms are what governs my success or failure of my photography. Another great example we see this time of year is frost. Frost is a great subject for photography, but doesn't happen every morning. Conditions need to be in the low thirties or colder and there has to be some moisture present to get a good hard frost. Without knowing what causes frost to form or the expected weather conditions you may just sleep through a beautiful, photogenic frosty morning and not even know it!
When weather is the background it is not necessarily the primary reason you are taking a photo, but it creates the mood or emotion in your photo. Fog or snow is a great example. A fresh coat of snow on the ground creates a pristine and clean feeling in a photo while a swampy morning fog can evoke spookiness and mystery. Taking advantage of each weather condition can change how a scene is perceived and what you are saying in your photo.
Time of Day
What time of day or night it is greatly impacts what type of weather you will see. Frost or steam and mist rising from a lake you'll see in the very early morning. Lightning is best shot at night. Usually thunderstorms are an evening phenomenon. Clear, sunny days can prove challenging for photos because of harsh direct sunlight. When I plan photo shoots I like to lean towards later in the afternoon and hope for partly cloudy skies, or even cloudy skies.
Natural Lightning (Understanding Cloud Cover)
Everyone with a camera knows just how important the right light is in a photo. Knowing how much natural light expected during the day makes the difference in a washed out, over lit scene in bright sunlight, or an evenly exposed landscape under overcast skies. Sunrises and sunsets depend totally on the available light versus cloud cover. No clouds at dawn or dusk can equal a quick and fairly simple sunrise or sunset, but if there are a few scattered low clouds after a passing cold front, or perhaps a sheet of high, thin, translucent clouds capable of reflecting the sunlight back in glorious reds and oranges.
Its not easy in the least to understand weather forecasts. I happened to have been a meteorology major for a year of college, dated a meteorologist years ago, and have been interested in weather since I was a young child so I'm an exception to the rule when it comes to the general public's knowledge of the weather. However, that being said, if you desire to become good at your photography you must educate yourself on basic forecast understanding and where to find that information. Its not a simple task and it means more than just watching the weather channel. My suggestion is familiarize yourself with the NOAA website. That website is no-BS, as I like to put it. Its not about commercialism, ads, or starry looking meteorologists. Browse around your zipcode area and look at the additional weather information found at the bottom of the page. Another great website is Weather Underground. It blows The Weather Channel out of the water and seems to be far more accurate and detailed for small, rural areas.
So the next time you are tuning out the weatherman stop and think of your camera and the opportunities he is trying to clue you in on! You'll be a better photographer for it.