Is the timing of vomiting fixed i.e; you vomit only during practice, kindly note this thing. Is there any relation to intake of meals and also the amount of vomitus is significant. This is indeed right that hot weather may cause you to vomit at practice but still you need investigation and a physician consultation because there may be some root cause vomiting and the hot weather is acting simply as a trigger. kindly look for the content of vomitus if it is solid, liquid bile or blood stained. Also see there is any weight loss because your physician will ask you all these questions and then you may have to get a abdominal USG done and also endoscopy to arrive at final diagnosis. I am writing all this as a routine examination only so don t worry just go ahead n take care