The climate of Pamplona during the festival of San Fermin varies widely. Usually it tends to be hot and dry, but some years the weather has been rainy and cold, particularly late at night or early in the morning. To plan for your trip to Pamplona, check the forecast for this year at the following website: Weather-Spain.com
If you plan to watch the running of the bulls, do not forget to bring a sweater or jacket, because while you wait for the run, it can be chilly.
Usually the mornings are temperate but the afternoons are hot. If you are going to watch the bullfights in sun section, the weather may be pretty hot…. but don’t worry, you can bet on having someone nearby to offer you a cool sangria.
Note that though the weather during the day is usually warm but pleasant, evening can be cool so pack a jacket or light sweater and something to wear over your white shirt in case of rain!
My recommendation for women who will go to the bullfights or want some relief from the heat of a crowded bar at night is to buy a fan at one of the many shops that sell them in Pamplona. It will be a useful item that doubles as a great souvenir!!