烈日 literally combines 烈 (liè), meaning 'intense,' 'fierce,' or 'scorching,' and 日 (rì), meaning 'sun' or 'day.' Together, they form a vivid noun describing the sun at its most blazing, oppressive intensity—typically during midday in summer. It evokes heat so strong it can wilt plants, dry soil, or make outdoor activity exhausting.

This word is commonly used in descriptive writing, weather reports, and everyday speech to emphasize extreme solar heat—not just 'sunshine' but dangerously hot sunlight. It often appears in phrases like 烈日当空 (scorching sun overhead) or under 烈日下 (under the scorching sun). While poetic, it’s also natural in spoken Chinese when complaining about heat or warning others to take precautions.