You have six weeks of growing season to go, which is about how long a dose of fast fertilizer can last. I would fertilize again because you should get more bloom into early November. I don't know of any evidence that fall fertilizer compromises hardiness. I always fertilize in September. The heat doesn't matter as long as the plants are growing. But if they are stunned by heat and drought, they can't use fertilizer, and it could be harmful..

With similar weather here recently, fed the roses in 2 to 15 gallon pots with Neptune's Harvest 2-3-1 Fish & Seaweed fertilizer last week when the heat cranked up again into the 90's. Like you, wanted to give the milder weather-induced flush of buds every chance to bloom well. First watered & an hour later around 10 am (85), fed diluted Neptune's at 1.5 tablespoons per 1.5 gallons of water (the capacity of my watering can), at the rate for houseplants. Temps hit 96 that day & the roses were fine with that. Next morning the leaves looked fresher, as if the roses were saying "Thanks, we needed that!" Roses planted in the garden will get the same boost tomorrow & would have been fertilized at the same time if the latest round of weeding had been done then. Typical treatment here this time of year.

Figure this low amount of organic nitrogen feeds new growth that's happening anyway, rather than stimulating it. The roses are going to bloom now (and perhaps again), so may as well fortify them while they're expending that energy on flowers. Won't deadhead the Fall blooms, letting those that form hips do so. The phosphorous & potassium, along with the micronutrients, strengthen canes & roots for Winter hardiness.

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Thank you so much, this is helpful information.

Are we talking about a liquid foliar feed? If it's in the 90s you shouldn't spray ANYTHING on the leaves or they can burn. I like the temps to be in the 70s when I use any types of sprays.

As for fertilizing in the fall I do it all the time. The roses keep growing as long as the temps allow so there is no way to prevent late growth that will be lost to winter. I'd just as soon keep them fed so they can go into winter with good stores of energy for next spring.

Thanks Seil, I wasn't talking about a foliar fertilizer.

Sara, Thanks for asking this question, I was wondering about the same thing. I will do the same today. I am off today! :-) Happy gardening and more blooms! :-)