Which atmospheric condition can affect rocket performance during launch?

The performance of a rocket during launch is influenced by several atmospheric conditions, notably humidity levels and temperature gradients.

Humidity levels can affect the air density and, consequently, the aerodynamic characteristics of the rocket. Higher humidity suggests more water vapor in the air, which can reduce air density compared to dry air. This change in density can impact the lift and drag forces acting on the rocket, ultimately affecting its ascent performance.

Temperature gradients also play a critical role in rocket performance. Variations in temperature can lead to changes in air density and pressure at different altitudes. A steep temperature gradient might create unstable atmospheric conditions and affect the rocket's trajectory and stability during launch.

Therefore, both humidity levels and temperature gradients are crucial factors that can significantly impact a rocket's performance, making this answer the most comprehensive choice. Clear skies do not inherently affect performance, as they mostly pertain to visibility rather than atmospheric dynamics.