Like almost everything about gardening, safe and successful work outdoors during hot weather depends on the gardener's mindset and self-knowledge as much or more as it does on gardening knowledge or skill.
Is there a catch to gardening from fall through spring? Depending on your local climate, environment, and garden, there might be a few. But the main one is sunlight.
In hot-summer California areas, the period of high heat from mid-or-late-summer until weather cools during fall is the slowest period of the year for gardening.