When choosing a time of year to visit Pamplona, weather shouldn't necessarily be the deciding factor – you really just need to figure out whether to go during the Running of the Bulls (July 7th-14th) or sometime during the rest of the year. In July, temperatures can hit 35 degrees Celsius easily (95 degrees Fahrenheit). Since the air is very dry, it’s important to stay hydrated, especially if you will be running with the bulls. Sometimes summer thunderstorms can break the heat, but storms are fairly unpredictable and shouldn't be relied on. You’ll want to bring lots of sunscreen but also an umbrella and waterproof shoes.

Winter is considerably cooler, with temperatures dipping down to the single digits Celsius (around 40 degrees Fahrenheit). Be sure to wear a few more layers than you think you’ll need when going out in the afternoon or evening, because it always gets colder as the night goes on. In terms of weather, perhaps the best time to visit Pamplona is spring or fall, when temperatures are moderate. You’ll also beat the crowds this way, though you’ll miss out on the July festivities.

The BBC’s five-day weather forecast is reliable, and here’s a useful Fahrenheit to Celsius Converter provided by the National Weather Service of Buffalo, New York.

Pamplona Weather - 5 Day Forecast