Schwarzer - retired from international football with Australia - did not hold back in a scathing rant against football's governing body when speaking at the Leaders in Sport conference in London.
The decision to award Qatar the 2022 World Cup has been heavily scrutinized and allegations of corruption in the process have been common.
Schwarzer is in a better position than most to judge the suitability of Qatar's hosting in mid-year claims, having played in the region for Australia on many occasions, and he has serious concerns if the 2022 World Cup remains in its traditional months.
"I've played World Cup qualifiers there in June and it is hot," Schwarzer said.
"I played a game in Oman in June one year and it was 43 degrees (Celsius).
"Something needs to happen to stop games at that time of year. It is just ridiculous, and it will only happen once probably not just one person, but two or three people drop dead.
"That's unfortunate, but that's probably the only way they will do anything.
"It's ridiculous, it really is ridiculous to be playing at that time of year and I don't know why there's even a debate.
"A committee went out there and said it was not safe to play, yet they were still awarded it."
Schwarzer also said that FIFA's credibility from people within football was exceptionally low, and criticised their handling of the Garcia report.
Michael Garcia was tasked to head up an independent investigation into allegations of bribery in the process that saw Qatar beat Australia and other countries to win the 2022 hosting rights.
FIFA will not make the report public, though, and Schwarzer questioned that call.
"I find it really, really disappointing to see a global body that has so little trust globally, from anyone - even the members of the game," he added.
"And now there's this Garcia report. Why conduct a report if you are not going to make it open?
"If you want trust in FIFA, surely you should open the report and say 'here it is'."
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