I've used safbrew T-58 a couple of times over the last year and had both great batches and very yeasty-tasting batches.
Could the heat be the reason for the yeasty taste? A warm day in the Israeli summer can range 26-32C (78-90F).
The "yeasty" taste is most likely due to the ester production of the yeast. Esters can impart a variety of flavors, including banana, pear, plum, fruitiness, bubblegum, apricot, etc. A number of factors control ester production:
Any one of these factors could lead to a yeasty flavor, and all of these can vary greatly from batch to batch, depending on how consistent you are with your brewing process. In your case, high temperature is a prime suspect. Pitching rate and aeration are two other factors that can vary greatly between batches depending on your brewing practices.
Possibly, although "yeasty" is a tough flavor descriptor to get a handle on. T-58 is a Belgian yeast and has many flavors that are different from other yeast, no matter what the temp. High temps can exacerbate that. Frankly, if you can't keep the temp under 70, you should consider alternative methods of fermentation, like using a refrigerator or water bath to ferment in.