.Did you know that just before a storm, that the water flattens like glass,,, It is because of the low pressure settles all waves very quickly. If you watch closely as it approaches , one can watch it cross the lake, an awesome sight to behold.
Shakespeare includes the theme of weather (especially thunder) to show that something bad is happening, and to paint a gloomy and dark setting for the audience. Also, the thunder is only described right before Macbeth goes to meet the witches, which represents that the witches are doing evil and unnatural things that go against the norm. Similar to how thunder goes against the normal sunshine and happy weather.