March to May and October are the best months, with highs between about 21 and 28 degrees. April and May are also the busiest because the patios are in flower. July and August are the hottest, with highs around 37 degrees and almost no rain, and winter days are mild but wet from October to January.
Highs rise from about 21 degrees in March to 28 in May, with six or so rain days in March and April. The patios and gardens are at their best and the old town is busy.
What to wear: Bring layers and a light rain jacket, since mornings are cool and afternoons get warm.
Summer
19 to 36 °C · about 1 rainy days a month
Highs reach 33 degrees in June and about 37 in July and August, with almost no rain. Municipal museums and the Alcázar close at 14:15 in summer, so see them in the morning.
What to wear: Wear light cotton, a hat and comfortable sandals, and carry water.
Autumn
13 to 26 °C · about 5 rainy days a month
September is still hot at about 32 degrees, October settles near 26 and November near 19. Rain returns, with six or seven rain days a month from October.
What to wear: Bring a light jacket for the evenings and a waterproof layer from October.
Winter
5 to 16 °C · about 7 rainy days a month
Days reach about 15 to 17 degrees and nights fall to 4 or 5. It rains on six or seven days in December and January, but queues are short.
What to wear: Wear a warm coat and shoes with grip, since wet stone can be slippery.
If it rains
A wet day is easy to fill: the Mezquita, the Archaeological Museum, the Julio Romero de Torres Museum, the Caliphal Baths, the Calahorra Tower and Mercado Victoria are all indoors. The Judería lanes and the patios are best kept for dry weather, and Medina Azahara is mostly outdoors.
From June to September the afternoons are very hot, so do the outdoor sights early or after about 18:00. Medina Azahara opens in the evening in summer, which suits the heat. The Mezquita and the museums give cool breaks in the middle of the day.