The best months are November to February, when the Konkan is dry, daytime temperatures are around 28°C, and evenings are cool enough for a light shawl. This is also peak season — book ahead and expect crowded beaches on weekends.
March to May is hot and humid (35°C+), still feasible if you stick near the water. The monsoon runs from June through September and is the worst time for a beach trip — heavy rain, rough sea, ferries suspended — but the surrounding hills are spectacularly green and the Kanakeshwar climb is at its best then.