It depends on whether you are in Alaska, in mid-winter, at midnight, or in
New Mexico, at midsummer, at noon.

The temperature rise will not do any damage, not even to birds. The
reduction in efficiency due to increase in wire resistance will be
insignificant. Think in terms of 0.001 S-units.

Just turn up the powe to 1 KW and see what happens, if anything. It won't
fall down. The antenna length might increase by some fraction of one percent
due to thermal expansion. But your tuner will not notice any difference. The
difference is about the same as that between summer and winter,

Remenber that the wire has a very great surface area, over a length of many
feet, to dissipate the amtenna losses - and in a cooling breeze. It/s only
the relatively small antenna losses, roughly 100 watts, which have to be
dissipated - not the full 1000 watts.

Most of the loss and temperature rise occurs in the middle half of the
antenna. It is calculable but not worth the trouble. If it is enamelled
magnet wire the enamel will probably not be affected. Enamell is accustomed
to being in prolonged warm places.

The probability of doing any damage to anybody's property is less than
winning the national lottery with only one ticket. You may consider making
your antenna even more stealthy.

In general, the diameter of antenna wires is decided only on the grounds of
durability in adverse weather conditions. Here in the UK we are quite
fortunate - until Earth Warming tornados become more frequent.
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Reg, G4FGQ.