Summer - Like most European cities, August is a slow month as many of the residents are on vacation. At this time of year Valencia is extremely hot and humid with temperatures averaging between 30º-40º Celsius.
Fall - September and October are more active months and the weather permits beach outings. Sidewalk cafes are still open until around the end of October.
Winter - Though temperatures are still relatively mild, it´s too cold to sunbathe at the beach.
Spring - a lovely time to visit. The annual Fallas de San José unofficially mark the beginning of spring. Cafes and restaurants open their terraces and life spills out onto the street once again.
Valencia's official languages are Valenciano and Spanish. Valenciano is technically a dialect of Catalan but this is a polemic topic so it´s best to consider and call the local language Valenciano, as it is in many respects an independent regional language quite different in vocabulary and pronunciation to Catalonia´s. In the capital of Valencia, very few people only speak Valenciano and are not offended being addressed in Spanish. However, outside the capital, the principal language is often Valenciano and though many still speak Spanish natively, it is not the primary language. As in Barcelona, be senstive to this language dynamic.
English speaking skills of the locals can be hit or miss. Most people under 35 speak some English, and some quite a bit, but most would obviously prefer being addressed at first in Spanish (or Valenciano).