My city, Vancouver, has an average temperature of 20 degrees Celsius, clear skies, occasional rain, and very little bugs during the summertime. It is about as moderate as you can get. Korea, however, has a monster of a summer: the sun bombards everyone with unrelenting infernal fury; July and August bring typhoons that blacken the sky; mosquitoes run rampant, draining all blood in their path, and cicadas cry everywhere until they die, literally. For someone so used to moderate climates, Korean summers are just brutal. However, I stay in Korea during the summer, so I had to learn to deal with this rather harsh time of the year. Thus, I now find the appropriate time to address the most common issues during the summer and explore ways to deal with them.
With temperatures of up to 35 degrees Celsius, heat stroke and dehydration are more common than expected, and these will lead sluggishness and tiredness. Go find places that sell tang (Korean stews) - they are packed with nutrients that will get you going for the rest of the day. Samgyetang (chicken and ginseng soup) in particular is renowned for its energizing properties. If you cannot stand hot food, then try bibim naengmyeon (cold noodles mixed with spicy red chili sauce called gochujang) and mul naengmyeon (sour cold noodles in iced broth) as a refreshing alternative. Soft drinks should be avoided, as they are not suitable for hydration. Consume drinks with plenty of electrolytes, such as Pocari Sweat (Korean sports drink), and drink lots of water with it. For a real Korean treat, try patbingsu (shaved ice with sweet bean). Most cafés sell patbingsu, which come in big portions to share and depending on the region, in different flavors and styles.
Mosquitoes in Korea are incredibly annoying, borderline satanic, as they can keep you up all night with their buzzing and their itchy bites. The dorms in KAIST are decent at shielding out bugs, but from time to time, bugs can enter though. If you plan to sleep outside your dorm, then bringing some form of protection will be necessary. Alongside mosquito repellants, Korean supermarkets sell special devices that repel these buggers efficiently. They come in two forms: an electric coil or an electric pad loadable with odorless cartridges. If you cannot be bothered to buy these items, then you can always rely on some bug spray. Do not spray the whole room - just the windows, doors, or any place that mosquitoes are likely to enter. Lastly, keep a swatter or something similar nearby to smack the hellspawn.
Finally, Korea is subject to strong winds and heavy rain every summer. Since typhoons are very random phenomena, you can never know when one will hit. If you are in dorm, you may be warned to tape your windows to prevent shattering, so prepare some tape beforehand. When going out, always bring an umbrella or a raincoat, as flash rains are common occurrences. Most importantly, always check the forecast for typhoon patterns and precipitation.
As long as you watch out for the heat, bugs, and rain, and are amply prepared, then this summer should not affect you in any significant way. Most of these tips are common sense, but just remember what Korea has as a solution to these problems, and you can go through summer scotch-free.