You have to consider the weather conditions and the local customs when you are planning a trip to see a city like Sevilla. You want to go when the weather will be pleasant, and if at all possible you want to go when the locals will be celebrating festivals or other enjoyable activities.
The temperatures in this part of Spain can soar quite high during the latter summer months. From January to February you can expect mild temperatures close to sixty degrees. From March to April the temperatures rise to about seventy degrees each day. In May and June the temperatures get closer to eighty and ninety degrees, and by July they have soared into the upper nineties, and possible the triple digits. In late September the temperatures start their gradual decline. There have been some summers when this part of Spain saw temperatures reach as high as 115.9 in July. Plan your trips to the area according to what activities you like to do, and the heat factors. Do remember that if you travel in the hottest part of summer you should do outdoor activities in the early morning, and in the late afternoon, and do indoor activities during the heat of the day.
The precipitation in this part of Spain will not really affect your visitation schedule. On average this area has rained on about sixty-six days of the year. The majority of the rain falls between October and April, and December sees the heaviest amounts of rain.