Complex sentence: A hot haze softens the edges of the trees in the middle-distance and washes out colour from the bridges and factories in the background--the blue of the sky at the horizon is paled almost to whiteness.
Split into simpler sentences: A hot haze softens the edges of the trees in the middle-distance and washes out colour from the bridges and factories in the background. The blue of the sky at the horizon is paled almost to whiteness.