A working transit town rather than a tourist stop in its own right — Ma'an's importance is entirely about location, sitting at the junction where routes to Petra, Wadi Rum, and Aqaba split off from the Desert Highway. It was a key stop on the historic Hejaz Railway line, and the old station building is still standing if you're interested in that history.
Ma'an sits about 3.5-4 hours south of Amman (215 km) on the Desert Highway, the last major town before the roads split toward Petra, Wadi Rum, or Aqaba.
Not weather-dependent — it functions as a waypoint, so timing matters less here than at the destinations around it.
There's little reason to build time into an itinerary specifically for Ma'an beyond a fuel or food stop — its value is as a junction point, and most private drivers will already be passing through it en route to Petra or Wadi Rum.