A SIT traveler’s choice of seasons & travel dates are usually personal preference unless defined by restricted vacation time, school opening/closing or host country’s seasonal events (Hue, Vietnam’s “Hue Festival  every 2 years in April).

    A. When to travel advice:
         1) probability of your ideal desired weather. Elaborate online resources available:

         Source: Weatherspark: https://weatherspark.com/countries/s/JP/3#Figures-Temperature         

Weather is always a crap shoot

         2) avoidance of high-season’s ‘tourist’ congested chaos & inflated prices:  

              Anecdote: China: I scrambled during China’s 8 day New Year’s season to find a hostel bed
                     because many Chinese travel then & everything is pre-booked well in advance.

        3) avoid closure dates of site & activity. 

             Anecdote:  Antarctica: I traveled to Antarctica in March 2011 because  :
              a) I had 2 ½ months to kill after my US State Department removal from Egypt's Spring Revolution. 
              b) Antarctica ship rates lowest at the end of their October to March cruising season 
              c) Antarctica is always cold anyway.

   B. Seasonal:
I typically chose travel dates based on the seasons. 
         1) If USA’s winter season, I purposely chose countries near the equator, e.g. Ecuador is on the
              equator, OR , in the southern hemisphere’s summer season, e.g., New Zealand, 

         Anecdote:  Arizona to Argentina: I left snowed covered Tucson, Arizona (a rarity) in the winter, arriving in Argentina's, Buenos Aires warm early fall like weather. Ironically, part of my travels were in Chili's northern Andes where it was chilly.

        2) In USA’s summer, I would chose countries in northern hemisphere e.g.Europe, China, etc.
            Occasionally  N & S Spain & Portugal

        3) A purposeful MIX of seasons:

        Anecdote: Camino de Santiago trek, Spain: My late summer/early Fall Camino de Santiago trek had to
anticipate August’s central Spain’s rainy/foggy rolling-hilled vineyards. Then, Meseta Plateau’s chilly September early morning starts (6 am) & blistering treeless afternoons, ONTO west Spain’s high plateau’s cold Fall mornings & lovely middays.   

Deeper & deeper into the Camino de Santiago's flat Meseta   

       4) Late winter/early spring:  (???) so that I could minimize summers heat and avoid Summers tourist
           congestion.
                    Sometimes my clever 😇  planning worked. Sometimes it didn't. 

    Anecdote: Venice, Italy: I visited Venice in July because I would rather endure rsidul back surgery discomfort in Italy tah sitting at home. Unfortunately, I had to suffer hordes of tourist and 2 solid weeks of rain. 

You can't win them all.         Sometimes I just went when I could.

Reflection: Rapid world wide tourism growth, particularly during summer vacation, is rendering major sites jammed with multi-tour buses & cruise ships disgorging 1000’s into snaking globs of tour groups often accompanied by the cacophony of multiple guide’s screaming megaphones.

     Note: Royal Caribbean’s new "Icon of the Seas" cruise ship carries 7600 people. Imagine the destructive  impact on tourist areas. Iconic (pun intended) example of the destruction of authentic tourism. 

More major sites are mandating, tourist, headphones to try to reduce chaos and try to restore, a worthwhile tourist experience.

   C. Site Chaos Avoidance tactics.

        1) Super popular Tier 1 sites.  
              a) choose off season travel, but before site closes for off-season, if they do. K17 PIK: Coliseum

              b) Arrive well before 10 am & after 3:30pm when most tour & cruise folks leave. CAUTION: high
                   tour, bus volume May force, tour bus, companies to arrive earlier or leave later

              c) During peak tourist hours, plan visits to small, obscure sites AND walkabouts outside the
                  main tourists areas tourists tend not to go even when given free time.

        2) All sites:
              a) Arrive at or even before site opens: 

Anecdote: Mexico’s Teotihuacan ruins: purposely overnighting in nearby San Juan Teotihuacán town,  I arrived at the ruin's entry gate an hour before it opened and chatted with the gatekeepers. Suddenly, they asked if I'd like to go in early. Over joyed & shaing hands all around I enthusiastically thanked them and had these giant ruins and their pyramids to explore with no tourists.      One of my most rare and memorable travel experiences.

             b) Some sites may offer early access tickets. Sometimes
                 a little ‘baksheesh’ (mini-bribe) gets you in the door.

      Bus Tours/Cruises
Bus Tours/Cruises excursions have very INflexible site schedules to profitably fulfill tourist package promises; a complex business model.