When it rains!
When it's not one of the 300 days of sunshine... it is certainly worth checking the forecast including the rainfall radar. The locals might advise: "If it's raining wait 5 minutes and the sun will be out". Alternatively if it's hammering down with Sahara sand leaden rain then it may be worth jumping in the car and heading twenty minutes up or down the coast.
The Sierra Bernia can often trap weather systems North or South. Pictured here Altea on a rainy day in Moraira.