Moon

It has long been thought that rings around the moon are a sign of bad weather, and in most cases it's usually true. The rings often appear as a result of light passing through ice crystals in a cirrus cloud at a very high altitude. These type of clouds are often followed by a warm front and low pressures that create storms.

As well as the above, folklore suggests that the number of stars that can be seen within the halo will be an indication of how many days remain until the storm arrives.