This is the largest and most populated island of the Azores. There is a vast array of things to see and do and also a better selection of accommodation and restaurants here than the other islands.
The Azores benefits from a temperate maritime climate with some fluctuations in weather patterns. July and August are the warmest months with pretty much sunshine all the way, but it's not necessarily guaranteed as the Azores experiences what's called Mares de Agosto or August tides. Infrequent warm front storms do blow in bringing high winds and high waves. It usually blows over fairly quickly though and you could have sunshine and rain all in one day. The high winds that do hit the Azores can cause delays on Azores flights and ferries, so be prepared for that.
The rainy period falls in April and May, with January and February the coldest months.
Annual median air temps on the Azores are 17 degrees centigrade. During the colder months of Jan/Feb temperatures rarely fall below 13 degrees centigrade. In the hotest months of July and August average air temperatures are 22-23 degrees centigrade so not oppresively hote!