While you might be lucky and have sunny and warm weather, I would recommend to be prepared for cooler weather as well. Take T-Shirts, but do not forget a sweater and/or a jacket. You might have pleasant temperatures in the 70s during the day, but at night temperatures might drop to the 40s. The probability for warmer weather is higher in Almería than in Madrid, but neither there, you can totally rely on being able to wear summer clothes all the time in October. And Granada can definitely get chilly at night, too, since it is in a mountaineous area.