the data sheet puts thermal resistance to air at 65C/w ... so lets round your .87 up to 1w ... that means the body of the regulator will increase 65C over ambient with 1 watt of power dissipation.
If you're in a cool room, 25C, that's well withing the 125C operating temperature. Even if it is hot out, like 35C, you're still within spec.
however, 90-100C is damn hot. even a small heat sink would make the regulator safer to work around, in case you touch it, you don't get a nasty surprise.