Which of the following is a common sign that a fire might be becoming unmanageable?

High winds shifting direction is a common sign that a fire might be becoming unmanageable because wind plays a critical role in the behavior and spread of wildfires. When winds are strong and unpredictable, they can rapidly change the direction in which fire spreads, making it difficult for firefighters to control. Wind can carry embers long distances, igniting new fires far ahead of the main blaze. This creates multiple fronts that need to be managed and can result in a situation where resources are strained, and containment efforts are significantly challenged.

In contrast, cool temperatures at night typically slow down fire activity, providing a brief respite for firefighters to regroup. Heavy rain before the fire season generally helps to increase moisture levels, reducing the risk of wildfires starting in the first place. Low humidity levels can contribute to increased fire danger, but on their own, they do not indicate that a fire is already out of control as effectively as shifting winds do.