In this paper I reflect on the concept of affective atmospheres in the context of the distinction between affect and emotion that has emerged in recent work on emotion, space and society. The concept of atmosphere is interesting because it holds a series of opposites -- presence and absence, materiality and ideality, definite and indefinite, singularity and generality -- in a relation of tension. To develop this account of atmosphere I juxtapose Marx's materialist imagination with a phenomenology attentive to singular affective qualities. By invoking a material imagination based on the movement and lightness of air, we learn from the former about the turbulence of atmospheres and their indeterminate quality. From the latter, we learn that atmospheres are singular affective qualities that emanate from but exceed the assembling of bodies. As such, to attend to affective atmospheres is to learn to be affected by the ambiguities of affect/emotion, by that which is determinate and indeterminate, present and absent, singular and vague.