Which flag size is designated for use in stormy weather?

The storm flag is specifically designated for use in stormy weather conditions. This flag is smaller in size compared to the garrison and post flags, which makes it more suitable for display during adverse weather conditions like high winds and rain. The design and size of the storm flag allow it to withstand harsher environments, thereby preventing damage that larger flags may incur in such weather.

In contrast, the post flag and garrison flag are intended for use in clear weather and are displayed on occasions when the weather is favorable. The battle flag, while also significant, is typically associated with military history and specific contexts rather than with weather conditions. Therefore, the storm flag is the appropriate choice for stormy weather as it ensures visibility while being durable enough for challenging conditions.