Understanding 'Serenity' in Context

Read the following passage:

Despite the tumultuous weather outside, Clara felt a profound sense of serenity as she sipped her tea by the window, watching the droplets race down the glass. The storm was fierce, yet she was untroubled, immersed in her thoughts. This feeling of tranquility was rare for her, often interrupted by the chaos of daily life. In this moment, she embraced the peace that prevailed in her mind, a stark contrast to the raging storm beyond.

What does the word serenity most closely mean in this context?