Which of the following contributes to high density altitude conditions?

High density altitude conditions are significantly influenced by temperature. When temperatures rise, the air becomes less dense because warmer air can hold more moisture and expands, leading to a decrease in air density. This reduced air density means that aircraft performance can be adversely affected, as engines may not produce as much power, propellers may be less effective, and lift generated by the wings may be reduced. Therefore, high temperatures contribute directly to an increase in density altitude, which can pose challenges for pilots during takeoff and landing operations, especially at high-elevation airports.

In contrast, high air pressure typically leads to lower density altitude by compressing the air, which increases its density. Low humidity also contributes to lower density altitude conditions since drier air is denser than moist air. Lastly, low elevation corresponds to lower density altitude, as density altitude is typically lower at sea level. So, the primary factor here that directly correlates with an increase in density altitude is high temperature.