Extreme temperatures
There are four seasons in South Korea, all of which have extreme temperatures. In the winter, despite there only being about a month of snowy days, the temperatures can drop to near-freezing and stay that way for several months. When summer rolls around, it can be scorching hot and unbearably humid, even for the locals.
Make sure you dress appropriately for the season. When it’s hot, short sleeves and short pants are the norm. When it’s cold out, short pants (remember?) and long sleeves with coats are suitable winter wear. When it rains, always take an umbrella with you. You can even “park” your umbrella in special storage compartments outside of convenience stores before entering.