depends on yr building rules...but you can get a shade cloth
like this from amazon:
https://tinyurl.com/m6pwzpmh
it says it cuts down wind and reduces temps by 15F ...
provided you can zip lock it to yr railing. it should really help.
keep in mind that square pots do not fall and roll as easy as round ones. and in FL people put plant pots in larger pots (2" + diameter, so at least 1" in-between, that helps to keep roots cooler. also you can't use dark color pots: they heat up tremendously. if you can't replace yr pots with white ones, even just painting them helps too.
getting white painted slat boxes (like for patios) to put pots in will serve the same purpose. cooler pots will need less watering.
if you do the above it will increase your choice of plants a lot! otherwise you'll need to look at xeroscaping choices like yucca, agave, mangave, aloes..nothing else will survive for long.
