Small but powerfully painted, Summer Condition is an excellent example of Hanly's gestural expressionism. With the word Summer emblazoned in thick yellow paint across the foreground, it maintains a representational division into sky, vegetation and earth. Following tuition at the Canterbury College School of Art and a period working in Wellington, Hanly travelled to London where he studied at the Chelsea School of Art, and lived with fellow New Zealand artist, Gil Taverner, from 1958 until 1962. Returning to Auckland, he began teaching drawing at the School of Architecture part-time, which he continued to do for the next thirty years, while painting and exhibiting prolifically.

Hanly's work from the 1960s and early 1970s celebrate his return to the Southern Hemisphere. He relished having time to paint during the hot summers after the teaching semester ends in November. He created many joyous depictions of the abundant growth of partner Gil's lush tropical plantings in the Windmill Road garden. Here in Summer Condition, Hanly energises relationships between aspects of the garden with vibrant daubs of paint. In another work from the same year, Summer (1974) in the Jasmax Collection, he uses the same dark cerulean blue for the sky, interrupted with lighter blue cumulus cloud patterns. The primary colours of blue and yellow enhance each other, tying the painting together vertically. The complementary secondary colours of green and orange link together horizontally to tighten the composition.

1974 was a watershed year for Hanly. A retrospective exhibition of 52 paintings from 1958 to 1974, organised by the Dowse Art Museum in Lower Hutt toured the main four centres as well as Hamilton and New Plymouth, arousing huge interest and commentary, establishing him as one of the leading painters of his generation.