When is the best time to pray Duha in winter, analogous to the preference for praying it in summer "until the ground warms up for the young camels"?

The preferred time for the Duha prayer is after the sun has risen and a quarter of the day has passed. This is its best time, although it is permissible from sunrise until zawal (the sun's declination from its meridian). This is supported by the hadith (definition): "The prayer of the oft-returning (Awwabin) is when the young camels feel the heat of the sun (tarmadu al-fisal)," which means when the sun's heat becomes intense for young camels. This is the middle time between sunrise and zawal.