A heat warning was issued for many parts of South Korea on Friday, with midday highs soaring to 32-33 degrees Celsius in Seoul and other cities. Along with the heat wave came a high concentration of ozone, prompting authorities to advise the old and weak to stay indoors.

According to the Korea Meteorological Administration, heat wave alerts were issued at 11 a.m. for Seoul and several other cities, which were expanded to the entire Gyeonggi Province and many cities in Gyeongsang, Jeolla and Chungcheong provinces between 1-2 p.m. 

A heat wave warning is announced when daytime temperatures are expected to reach 33 degrees and above for two straight days. For Seoul and most other cities, it was the season’s first issuance of the alert.

The southeastern city of Daegu saw the nation’s first heat wave warning last month, when the daily high reached 35 degrees.

With the heat wave warning in place, elderly and children were encouraged to avoid the sun and stay hydrated.

The weather agency also issued an advisory for ozone across the city of Seoul at 2 p.m. High levels of ozone in the air are known to cause difficulty breathing, indigestion and nausea.

By Bak Se-hwan (sh@heraldcorp.com)