I want to run away somewhere. Muggy summers tend to put you in that kind of mood.

Literal

Somewhere [to-へ] escape-trip want. Humid-hot summer [topic-は] that-kind-of mood [to-に] become-tend-to.

逃避行 (flight/escape journey) is a dramatic compound — 逃避 (escape) + 行 (journey). ~がち (tends to) marks a habitual tendency, often with a slightly negative nuance. 蒸し暑い (muggy/humid and hot) is the standard term for Japan's oppressive summer humidity.