While there is no clear indicator for weather by the eye, it is possible to recognize an existing potential within a system, especially with clouds. Clouds - as many know through experience - are the one factor that remains consistent through any weather event. It is more than likely that if the day or night is clear, there is little chance for the possibility of a bad weather system. However, the ability to recognize clouds and their association with the varying weather types relies more than just sight alone.
There are few people who are not aware of the meaning behind a dark cloud on a day of any season, that if it isn't going to precipitate at the moment then it is only a matter of time. These dark clouds are so because they contain more built up quantities of ice crystals at their tops that will soon become too heavy for the updrafts from the earth to support before they are free to fall. If the air between the ground and cloud is warm, that ice melts and forms rain or remains as ice called hail, while if the temperature is cold it falls as snow. This easily recognized darkness is just one of the simple sight indications of a bad weather cloud.
Along with dark clouds others colors serve as important warning indicators. Clouds tinted with reds can allude to cyclonic activities, while clouds with green can be known hailstone carriers. The size and motion of the clouds are important visual indicators as well, where a large and fast moving, dynamic, fluid-like cloud can indicate the potential for high winds and clouds with slow rotation can become a precursor for tornados. There is little need for clarifications when it comes to funnel clouds; they are one of the deadliest forms of bad weather clouds!
Apart from sight there is another method that alludes to the formation of possible bad weather even if you are unable to see outside. This is method is through the sense of touch. Though not a completely accurate detection method, it can sometimes precede the sense of sight by serving as an early warning system for the approach of bad weather clouds.
Going back to the formation of precipitate; as clouds move along and are accompanied by strong updrafts and downdrafts they build charge through the interaction of the ice within. As bits of ice are forced upwards they encounter the heavier ice pieces that are pulled or fall downwards, colliding and scraping a layer of electrons off the upwards traveling piece. With the increase of smaller positively charged ice pieces at the top and negatively abundant charge at the base of the cloud, a charge difference occurs. This charge is the first of several necessary steps for the formation of lightning.
The build up of charge is not isolated to the clouds only. As the tops of the clouds form a positive charge and the bottoms form a negative, a positive potential is also formed in the region close to the ground and moves along with the negatively charged clouds. Like a capacitor the cloud forms one plate while the ground forms the other, with the air as a perfect insulator between the two. When the charge builds too much, a dielectric breakdown occurs between the clouds and ground and a lightning bolt is born. It should be noted that this positive charge will often travel up higher objects to narrow the gap, which is why higher objects are struck with greater probability.
This formation of the two charges is important because humans and many other animals actively generate weak electric fields around their bodies that are virtually invisible to their own sense of perception. However, when large storms start to form and travel into an area, the large positive charge that travels beneath it interacts with the living organisms and their individual electric fields. This is why many animals with keener senses are wary of storms and seek shelter and why people feel differently in pre-storm conditions. Others with old injuries that had damaged the electrical connections at points of the body (nerve networks) feel pain and unease in their old wounds before it rains. This is mostly because of the heightened clash of electrical charge potentials interacting. It should be noted that once the rain and lightning starts the feelings tend to dissipate because the positive field begins to lessen.
Other aspects of sight and touch are less devoted to the effects of the clouds and more to the winds and their interaction with the surrounding environment. Aside from sight and touch; smell, taste, and hearing can be demonstrated in lesser degree, but usually not so much with the clouds as the effect of the storm system itself. In the end it is mostly the sense of sight which is the universal identification method for bad weather producing clouds.