Hi, and thanks for the input!
You're right, temps have been in the ( ... digs out calculator to convert degrees F to C and back again ... ) low 90s F, but it's a rooftop apartment and catches full sun, and so acts like a brick oven ... heats up all day and throws it back all night. Without A/C, the temperature can get up to >40C / >>100F.
But your advice is well-taken. Maybe I'll look into heat-tolerant species, and also work out exactly how much the A/C costs.