The New York-based organisation also called on the Gulf state to investigate workers' deaths and make those findings public.
"The Qatari authorities' failure to put in place the most basic protection from the heat, their decision to ignore recommendations that they investigate worker deaths, and their refusal to release data on these deaths, constitutes a wilful abdication of responsibility," said report author Nicholas McGeehan.
He also called on football's world governing body, FIFA, national associations and World Cup sponsors to demand further protection from heat and humidity for Qatar's workers.
McGeehan added: "They should also be demanding answers to two simple questions -- how many workers have died since 2012 and how they have died?"
Qatar has introduced laws to stop people working outside between 11:30 am and 3:00 pm annually from June 15 to August 31, when temperatures can reach around 50 degrees Celsius (122 degrees Fahrenheit).
But HRW says these measures do not go far enough.
"Limiting work temperatures to safe temperatures -- not set by a clock or calendar -- is well within the capacity of the Qatari government and will help protect hundreds of thousands of workers," said Sarah Leah Whitson.
Temperatures in Qatar are currently in the high 30s Celsius and humidity levels are above 50 percent.
The HRW says medical research suggests heat stress is a genuine risk to those working outside, and it has called for greater flexibility by Qatari authorities.
In rare praise for Qatar's World Cup organisers, it said the government should follow the example of compulsory work-to-rest ratios introduced for the 12,000 helping build venues for 2022.
"If Qatar's World Cup organisers can mandate a climate-based work ban, then the Qatar government can follow its lead," added Whitson.
However it called for much greater transparency by Doha on the vexed issue of worker deaths.
It said figures were last made available in 2012.
Out of the 520 deaths then for workers from Bangladesh, India and Nepal, 385, or 74 percent, were "neither explained nor investigated".
The HRW said there had been 10 deaths reported by World Cup organisers between October 2015 and July 2017, eight classified as "non-work related".