July is the hottest month in Mykonos with an average temperature of 26°C (79°F) and the coldest is January at 9°C (48°F) with the most daily sunshine hours at 14 in July.

The hottest month in Mykonos, Greece, is typically August, though July is a very close second. During these peak summer months, daytime high temperatures consistently average around 28°C to 30°C (82°F to 86°F), but "heatwave" spikes can frequently push the mercury above 35°C (95°F). The heat is often tempered by the Meltemi, a strong, dry northern wind that blows across the Aegean Sea in the summer; while this provides a cooling breeze, the sun remains extremely intense with a "Very High" UV index. August also sees the warmest sea temperatures, averaging around 25°C (77°F), making it the prime time for beach clubs and swimming. However, it is also the most crowded and expensive month of the year. For travelers who prefer warmth without the extreme peak, September offers a "mellow" heat with daytime temperatures in the mid-20s and much smaller crowds. If you visit in August, it is vital to book air-conditioned accommodation and plan outdoor sightseeing for the early morning or late evening to avoid the scorching midday Mediterranean sun.