Þingvellir National Park in December

June through September gives you the warmest weather and longest daylight hours - perfect for hiking and photography. July and August are peak season, so expect crowds at the main viewpoints by midday. Early morning visits (before 9 AM) or late afternoon (after 4 PM) offer better lighting and fewer tour buses. September is actually ideal - you get autumn colors, fewer crowds, and still decent weather. Winter visits have their own magic with snow-covered landscapes and potential Northern Lights, but daylight is limited and some trails get icy. Spring (April-May) can be muddy as the snow melts, but you'll have the place mostly to yourself. The park is open 24/7 year-round, so you can visit for sunrise or sunset shots.