Employee worked for about 30 mins packaging product in super sacks then started to clean for 60 minutes. EE felt light headed & went to get a drink of water. Went back to work. EE felt light headed still so EE stood in front of a fan. EE was then helped to the break room. EE felt overheated. The temperature outside was high of 100. EE had hiked the previous day. EE was dehydrated.