May and June: the best compromise
The sea passes 20 degrees in May and reaches 24 in June. The air sits between 25 and 30, warm without being crushing. The first pool parties open in May, the boat party season starts in June, and the Paceville clubs already run every weekend. Accommodation prices stay well below July. For a lot of people this is the best window of the year.
July and August: the peak, and the crowds
Thirty-two to thirty-five degrees by day, a sea at 26, no rain. This is full Maltese summer and everything runs at capacity: complete programming in every club, boat parties several times a week, festivals. It is also when the beaches saturate, prices double and nights need booking ahead. The heat is dry but real: days happen in the shade or in the water, life resumes in the late afternoon.
September and early October: the insider window
The sea is at its warmest of the year, around 26 degrees, heated by the whole summer. The air drops back to 28 or 30. Clubs still run through September, and the season-closing nights are often among the best. Prices fall noticeably after mid-September. If you only remember one month, make it this one.
October to April: the island without the parties
The weather stays mild, 16 to 22 degrees, with the year's only real rain between November and February, in short bursts. The sea turns cold from November. On the nightlife side the programme thins sharply: a few Paceville clubs stay open at weekends, but pool parties and boat parties stop. It is a beautiful time to visit the island, not to come and party.
The wind, the thing people forget
Malta is exposed, and wind changes plans more often than rain does. The majjistral, the north-westerly, can turn the sea rough overnight and cancel a boat party or a Comino crossing. It happens mostly in spring and autumn. If your trip hangs on a trip out to sea, keep a backup date.