Summertime in Spain means that much of the country is bathed in glorious sunshine, but that doesn't mean you won't catch some rain on any given day in June. The famous song from "My Fair Lady" promises the rain in Spain stays mainly in the plain. But that can't be depended upon; while Spain doesn't get as much rainfall as other European countries, a little rain is a possibility at any time of year.
June in Barcelona
June is a great time to come to Barcelona because the extreme temperatures of high summer haven't arrived yet, but it is still warm enough to sunbathe on the beach or to enjoy a beer on a terrace. The weather in Barcelona in early June is excellent, invariably in the 70s F during the day with cool but pleasant temperatures at night that range from 57 to 66 F. Rain is possible but unlikely. By mid-June, Barcelona's weather has crept a few degrees higher, with daily high temperatures hovering around 80 F with nighttime temperatures around 64 F. It tends to be dry. Late June tends to see Barcelona's weather get even warmer, sometimes approaching the mid-80s F, with nighttime lows rarely dropping below 64 F.
June in Madrid
The weather should be hot and dry in Madrid in June. However, the Madrilenos have an expression that is worth noting: "Hasta el cuarenta de mayo no te quites el sayo." ("Until the 40th 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, because the rain may come back.
The average daily high in Madrid in June is 82 F, with the nighttime temperature dropping to a pleasant 55 F.
June in Andalusia
June is one of the best times to visit Andalusia in southern Spain. The weather is usually hot but not to the dangerous levels it can reach in August, with minimal rainfall.
The average high in June in Malaga is 81 F, with the average low 63 F.
June in Northern Spain
Northern 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. If you like a bit milder weather, you'll like northern Spain in June, where the average daily high in Bilbao is 72 F, with the average low 57 F.
June in Northwest Spain
Galicia and Asturias are heading out of their very wet season, into plain old wet in June. If you're elsewhere in the country and are heading to northwest Spain, check the weather forecast before you go. Temperatures are rising in June but you can't rule out some wet and chilly days. The average daily high temperature in Santiago de Compostela in June is 66 F, with the average low 57 F.