Things to pack when travelling to Madrid:

Clothings:

The weather in Madrid can either be chilly or hot for the seasons are fairly distinct (during August it can be uncomfortably hot). But it also seems to be showing evidence of our climatic change on the planet… at the moment, and for much of my time here so far, sudden downpours can appear even on a hot sunny day. If you use umbrellas, you may want to bring one along, or a jacket and a coat.

Comfortable shoes for walking are but vital. The nature of the city, with its many winding streets, occasional steep hills and the endless stairs in the Metro system means your feet should be able to bear all these so comfy shoes are a must for travelers.

Depending on your personal preference, and the kind of places you want to visit, you may consider that shorts and sandals are less seen in the city, even under a hot weather. It’s considered more suitable to be worn at the beach. Some of the pricier discotecas/salas or nightclubs may not allow entry to men wearing trainers or jeans.
Toiletries and Medical Supplies:  The weather could be hot in Madrid so it is highly recommended to bring some sunscreen or sun block.
Miscellaneous: Also pack in a Spanish dictionary/phrase book.