Manipulating the weather isn't an issue for most pegasi. Controlling the weather is a job for a team of pegasi... unless you're Rainbow Dash. However, in areas where Harmony's influence isn't so strong or not even a factor, it shouldn't even be possible.

In such cases, Rainbow Dash might need some help. If the only help just so happens to be Spitfire who has focused her training on rescue operations and not weather operations, there are bound to be some issues.

In this case, Rainbow Dash isn't angry about the on-the-job training, but rather the difficulty communicating over the environmental hazards.