Spring (March-May): Ideal visiting season with mild temperatures (8-15°C), blooming flowers in parks and gardens, and fewer crowds than summer. St. Patrick's Day (March 17) brings massive celebrations but also inflated prices and packed accommodations. Easter offers long weekends but variable weather.
Summer (June-August): Peak tourist season with longest daylight hours (sunset around 10 PM), warmest temperatures (15-20°C), and numerous festivals. Expect higher prices, crowded attractions, and advance booking essential. Weather remains unpredictable with frequent rain despite being 'summer.' Best for outdoor activities and coastal day trips.
Autumn (September-October): Excellent shoulder season with comfortable temperatures, beautiful foliage in parks, fewer tourists, and lower prices. September often has better weather than summer. Culture Night (September) offers free access to museums and venues. October brings Halloween festivities (Samhain origins) but increasing rainfall.
Winter (November-February): Low season with shortest days (sunset around 4:30 PM), cold temperatures (4-8°C), and frequent rain. Significant savings on accommodation and flights. Christmas markets and New Year's celebrations add atmosphere. Phoenix Park's deer are particularly visible. Museums and indoor attractions are less crowded. January sales offer shopping bargains.
Dublin's maritime climate means weather is famously unpredictable. Expect rain year-round (average 730mm annually), often as sudden showers rather than all-day downpours. The saying goes: 'If you don't like the weather, wait 15 minutes.' Pack layers, waterproof jacket, and comfortable waterproof shoes regardless of season. Rarely freezing or extremely hot.