The Chink in the Armour by Marie Belloc Lowndes

Sylvia could hardly have said how it came about that she found herself established in the Villa du Lac only a week after her first visit to Lacville! But so it was, and she found the change a delightful one from every point of view.

Paris had suddenly become intolerably hot. As is the way with the Siren city when June is half-way through, the asphalt pavements radiated heat; the air was heavy, laden with strange, unpleasing odours; and even the trees, which form such delicious oases of greenery in the older quarters of the town were powdered with grey dust.