Spain gets genuinely, verifiably hot in summer, especially across the southern interior. Córdoba set Spain's all-time national temperature record of 46.6°C in July 1995, and Spain's national weather agency AEMET has recorded entire Julys as the hottest on record nationally, with daily highs regularly passing 40°C across Andalusia, Extremadura and inland Castile during peak summer. This isn't a mild warm-country stereotype — it's some of the most extreme heat recorded anywhere in Europe.
A dog's risk of heatstroke rises sharply in this kind of heat, especially on pavement and asphalt that can reach far higher temperatures than the air itself, and especially for brachycephalic (flat-faced) breeds, heavier-coated dogs, puppies, seniors and overweight dogs. Watch for heavy panting, drooling, lethargy, vomiting, or collapse — any of these during a hot walk is a reason to stop immediately, move to shade, and offer water, with a vet visit if symptoms don't resolve quickly.
The standard precautions matter more here than almost anywhere else covered in this guide: walk early morning or after sunset rather than midday between roughly May and September, never leave a pet in a parked car even briefly, carry water on any walk, and check pavement temperature with your own hand before a walk on a hot day. A dog that's struggled with heat before is at higher risk of it happening again, so err on the side of caution rather than pushing through a planned walk.