Verbseoul.
하다 verb (adj)
서늘하다seoneulhadato be cool, to be rather chilly

To say to be cool, to be rather chilly politely in the present tense, use 서늘해요 (suh-neul-hae-yoh). Below is the full conjugation of 서늘하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
서늘해
suh-neul-hae
서늘해요
suh-neul-hae-yoh
서늘합니다
suh-neul-hahm-nee-dah
Past
서늘했어
suh-neul-hae-ssuh
서늘했어요
suh-neul-hae-ssuh-yoh
서늘했습니다
suh-neul-hae-sseum-nee-dah
Future
서늘할 거야
suh-neul-hahl- -guh-yah
서늘할 거예요
suh-neul-hahl- -guh-yae-yoh
서늘할 겁니다
suh-neul-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
서늘하세요
suh-neul-hah-sae-yoh
Suggestion / Let's Polite (요)
서늘해요
suh-neul-hae-yoh
Question Polite (요)
서늘해요?
suh-neul-hae-yoh-?
Connective “and” — (고)
서늘하고
suh-neul-hah-goh
Conditional “if” — (면)
서늘하면
suh-neul-hah-myuhn
Noun form — (기)
서늘함
suh-neul-hahm