“How can cirrus and other clouds form without a storm coming?”
Cirrus clouds are the highest clouds and are made of ice crystals and tend to form 24-hours before a change in the weather occurs. Altocumulus clouds are mid-level clouds and thus can be made of ice crystals and water droplets. These clouds often form ahead of a storm bringing steady rain or snow. If you see these clouds on a warm, muggy morning you will likely see thunderstorms in the afternoon. Cumulus clouds are low level clouds and are made of water droplets. Fair weather cumulus clouds arrive with good weather, like their name implies, while cumulonimbus clouds can produce heavy rain, snow, hail, lightning and even tornadoes.