I try not to spray my oil/spinosad mix when temps are predicted to be 85 degrees or more for 4-5 days following the spraying.

During the summer months I have sprayed horticultural oils in the evening when it is cooler. The following days the temperature many times are in the 90s during June July and August. I've done it for years, without a single bit of damage the following day even on new flush growth. I use Ultra Fine Horticultural Oil, it comes in 2.5 gallon jugs.

Do you also a systemic like Bayer?

Don't use systemics.

Temperature and intense sunlight. Too much of any of these can burn the leaves. I've done it.

BTW: I've only applied systemics via the roots / soil drench... has anyone had success applying these via foliar spray?

Neem oil works well - 1/2 tsp per quart of water. I've been spraying it on my baby citrus trees 2x per week with temps up around 94 degrees (around 105 heat index) here in FL. I always spray at twilight though, around 8 pm and obviously avoid spraying on days that are forcast rainy as the oil will just wash off the leaves.