Early June in Paris is considered the beginning of the peak tourist season, so while it is lively and beautiful, it is definitely crowded. This period is highly popular because the weather is typically mild and pleasant (70°F/21°C), and the city's gardens are in full bloom. Major landmarks like the Eiffel Tower, the Louvre, and Notre-Dame (which is seeing massive interest following its 2024 reopening) will have significant queues, often requiring tickets to be booked weeks in advance. Additionally, early June often coincides with major events like the French Open (Roland-Garros) and the lead-up to the Fête de la Musique, which draws even larger crowds to the city. While it isn't quite as "stifling" as the late July heatwave rush, you should expect busy Metro trains and a "bustling" atmosphere in the Marais and Latin Quarter. For a more relaxed experience, it's recommended to do your sightseeing early in the morning and avoid the most popular areas on weekends when local Parisians and European weekenders add to the congestion.