This is the 669th most frequent Russian word.
сильно
"Сильно" means "strongly" or "intensely" in English.
In this sentence, 'сильно' is used as an adverb to intensify the adjective 'устал' (tired), meaning 'very' or 'extremely'.
Я сильно устал после работы.
I am very tired after work.
Here, 'сильно' functions as an adverb modifying the verb 'дует' (is blowing), describing the manner with which the action is performed, meaning 'strongly'.
Ветер сегодня дует сильно.
The wind is blowing strongly today.
In this case, 'сильно' is used as an adverb to provide context for the verb 'сжал' (squeezed), indicating the intensity of the action, meaning 'strongly' or 'forcefully'.