The weather in the region is mild and sunny: the nearest official weather records (indicative for the area) show summer averaging around 25 degrees, spring around 16 degrees, autumn around 20 degrees and winter around 12 degrees. Rain is scarce, especially in summer: on average fewer than three rainy days between June and August, against just over ten days in each of the other seasons.
The sea follows the same rhythm: averaging around 25 degrees in the summer months with a peak towards 27 degrees in July and August, around 22 degrees in autumn, and somewhere between 15 and 16 degrees in winter and spring. The busiest time of year coincides with the period when the Jávea town council runs a paid, barrier-controlled access system at the calas of Granadella and Portitxol, from June to early September.
If you want less of that crowd but still pleasant weather, the numbers point the same way: late May and June sit between the cooler spring and the heat of high summer, the sea is already warming nicely on its way to the summer peak, and the barriers at the calas do not go up until early June. September sits on the other side of that same peak, with a sea that is still warm and calmer calas once the barriers come down again in early September. The annual festivals, from the Fogueres de Sant Joan in June to Moros i Cristians in mid July, fall right in the middle of that high season, so anyone who would rather avoid the crowds should plan a visit just before or just after.