An Olympic athlete's spilling his guts on why he spilled his guts after a race ... blaming weather conditions after his race in Paris' Seine River -- NOT the water itself.
Tyler Mislawchuk -- the Canadian triathlete who went viral for all the wrong reasons when he hurled 10 times after racing Wednesday in the Triathlon -- says he's not used to such blazing hot weather.
ICYMI ... Mislawchuk's crossed the triathlon finish line and blew chunks within feet of his fellow competitors.