カッとflaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely

真夏(まなつ)の太陽(たいよう)がカッと照(て)り付(つ)けている。

The midsummer sun is burning hotly. {flaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely}

部下(ぶか)に悪口(わるぐち)を言(い)われて頭(あたま)がカッとなった。

I flew into a rage after being insulted by my subordinate. {flaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely}

信(しん)じられない光景(こうけい)を前(まえ)にして目(め)をカッと見開(みひら)く。

In the face of an unbelievable scene, my eyes flared open suddenly and widely. {flaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely}

暖炉(だんろ)に火(ひ)がカッと起(お)こった瞬間(しゅんかん)に、暖(あたた)かさを感(かん)じました。

The moment the fire flared up in the fireplace, I felt the warmth. {flaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely}

クラスメイトから悪口(わるぐち)を浴(あ)びせられたならカッとなるのも当然(とうぜん)です。

If you're subjected to insults from your classmates, it's only natural that you'd fly into a rage. {flaring up, burning hotly, suddenly becoming bright, flying into a rage, losing one's cool, opening suddenly and widely (e.g. eyes, mouth), acting resolutely}