While Spain doesn't get as much rainfall as other European countries, some rain is a possibility at any time of year.
Remember that we're talking averages here. Weather throughout the world is unpredictable, so don't take what you read on this page as gospel.
Weather in Madrid in JuneThe weather should be hot in dry in Madrid in June. However, the Madrileños have an expression that is worth noting - "Hasta el cuarenta de mayo no te quites el sayo" (Until the fortieth of May, don't take off your raincoat", that is, don't put your wet-weather clothes away until June 9, even if it looks like summer has arrived, as the rain may come back.
The average maximum temperature in Madrid in June is 82°F/28°C and the average minimum temperature is 55°F/13°C.
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Weather in Barcelona in JuneJune is a great time to come to Barcelona as the extreme temperatures haven't arrived yet but it is still warm enough to sunbathe and enjoy a beer on a terraza. In 2008, when I was in Barcelona at the start of the month, the city was just emerging from a drought - in a really big way! I've never seen heavier rain!
The average maximum temperature in Barcelona in June is 75°F/24°C and the average minimum temperature is 61°F/16°C.
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Weather in Andalusia in JuneJune is one of the best times to visit Andalusia. The weather should be really hot, but not to the dangerous levels it can reach in August. Rainfall is minimal in June in Andalusia.
The average maximum temperature in Malaga in June is 81°F/27°C and the average minimum temperature is 63°F/17°C.
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Weather in Northern Spain in JuneNorthern Spain is not as reliable as the south when it comes to weather, but you can be pretty confident that the weather in June will be mainly good, though there is a fair chance of rain for a few days each month.
The average maximum temperature in Bilbao in June is 72°F/22°C and the average minimum temperature is 57°F/14°C.
Weather in North-West Spain in JuneGalicia and Asturias are heading out of their 'very wet' season, into plain old 'wet'. If you're elsewhere in Spain and are heading to the north-west, check the weather forecast before you come. Temperatures are rising but don't rule out some wet and chilly days.
The average maximum temperature in Santiago de Compostela in June is 66°F/19°C and the average minimum temperature is 57°F/14°C.
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