What is one of the most easily recognized changes across a front?

One of the most easily recognized changes across a front is a change in temperature. As a frontal boundary moves through an area, it represents a transition between two different air masses, which typically have distinct temperature characteristics.

For example, when a warm front approaches, temperatures usually rise as the warmer air overrides the cooler air it is replacing. Conversely, a cold front typically brings a noticeable drop in temperature as cooler, denser air pushes out the warmer air. Pilots can often sense these temperature changes not only through their instruments but also by external cues, such as the sensation of warmth or coolness.

While increases in cloud coverage, relative humidity, and decreases in visibility can occur in the vicinity of a front, these changes may not be as immediate or as sharply defined as the temperature shift. The temperature change is often more conspicuous and serves as a primary indicator of a front's passage, making it a notable phenomenon for pilots to be aware of.