The phrase "a touch of fall" is correct and usable in written English.
It can be used to describe a slight or subtle indication of the fall season, often in relation to colors, weather, or atmosphere.
Example: "The garden was beautiful, with a touch of fall evident in the golden leaves and crisp air."
Alternatives: "a hint of autumn" or "a dash of fall".
He looks remarkably like a lugubrious Hitler, with a touch of mustache and hair falling over one eye, while in the background hovers the eagle symbol of the Third Reich.
Optical equipment maker JDS Uniphase caught a touch of Ciena's flu, falling about 4% in morning trading.
The spinach soup, with a touch of nutmeg and some cream, falls somewhere in between.
Some stories are light-hearted, such as "The Indian Child", a sprightly re-telling of A Midsummer Night's Dream; some have a touch of the supernatural, such as "The Fall of a Sparrow", in which the ghost of the Romantic poet John Keats puts in an appearance; some are tear-inducingly poignant, such as "Moving".
That might just be a touch of modesty -- Millepied fronted Club Monaco's Fall 2010 campaign, busting some moves in dapper suits.
When the Islamic rulers of Persia began hiring Turkic mercenaries about 800 ce, the soldiers brought with them a style of loose wrestling called koresh, in which grips may be taken on the long, tight leather pants worn by the wrestlers and the bout ends with a touch fall of the loser briefly on his back.
A young man with disheveled hair squatted on the ground, paintbrush in hand, adding golden touches of fall to his watercolor.
The many deaths and injuries that occur are shocking for the distracted scarcity of their narration, like the boy from Lancaster who "panicked above the crux of quite an easy route called Touch of Class and fell with a groan of fear backwards on to zinc grey boulders the size of commercial refrigerators".
