Baron Opal II
Legend
I believe the longest range of a PHB spell is "unlimited" (see Sending as an example). But I don't think that spell range is related to the question at hand.
I was thinking that if, barring spells like sending and gate, if there was a cluster of spells at a range of, say, 400 ft.* you could use that as a working maximum for the heat metal effect. So, maybe at 150 ft. the druid can't activate heat metal for that round? Eh, an idle thought of little consequence.Telepathy and Tsunami are "Unlimited"
Storm of Vengeance has "Sight".
Control Weather has a 5 mile radius but it's technically Self.
Next up is 1 mile mile for Clairvoyance.
And after that Arcane Gate, at 500 feet.
Then there's a few at 150 feet.
* Was that a 4e thing? Mostly four ranges of spells; touch, close (60), med (150), long (400)?