Weather-related questions.

"Can anyone let me know whether The Alps(hiking around Lauterbrunen), The Dolomites, The Tantras Mountain, will be much colder compared to their base area of nearby cities ?"

I wouldn't say "much colder", but rather, "not as warm". And usually never uncomfortably hot.

I would note that if you want to avoid the heat, in general, stay north of the Alps. Heat waves do occur, but they're usually short. Temperatures are usually comfortable for most of the summer. And if you want to avoid the "crowds" get ideas from outside the Rick Steves universe. Despite the perceptions on this website, you really can enjoy the Alps without hitting the Berner Oberland or Dolomite sub-range.

If you don't like the heat you could start in the south and end up in Oslo in August.

Just a suggestion.

Because mountains disturb the air passing over and around them, they tend to create their own weather patterns. In general, air can be 10 or 20 degrees Farenheit cooler higher up than at the foot of a peak. The air is thinner, though, and the sun's UV rays are therefore less filtered, so extra protection against sunburn and UV damage is prudent. As you noted, avoiding outdoor exposure when it's hot can help, and you may or may not have success finding air-conditioning indoors. Even higher up, or farther north, if you're in the sun it can be warm. Rain could also be more prevalent in mountains.

You might take a cue from the Spanish and have a fan (either an old-fashioned hand fan that you wave at yourself, or a battery operated model that might be too fussy and/or inefficient) to cool down a warm situation.

Weather.com will show you more detailed history, but you have to dig, for instance, click on "more forecasts," then choose "monthly." Different Greek islands could vary, but this past September in Crete, for instance, daily high temps averaged 82 degrees but one day went up to 93.

I completely understand your aversion to heat. Based on my experience living on the eastern edge of the Mediterranean, I'd expect much better weather in Greece and Rome (is that one of your destinations?) in May than September or even early October. I'd start there, then through the mountains. June is likely to be cooler in the mountains that July-August. England is hit-or-miss. I've been in hot dry weather in August and cold rainy weather in July. It will certainly be cooler than Greece or Italy. I don't think it ever gets really hot in Scandinavia so I'd try to fit that into July-August.

Thank you for all your replies.
Yes, I will like to spend more days in Italy, Sw3itzerland and Greece, for the Greek Islands.
Looks like I cannot escape the heat of July and August no matter where I travel first and I think June and September is too warm for me too in some areas. I will and try to minimise the "heaty" days in this pattern, please check and advise.

Mid-June till first 1/2 of July - Arrive Oslo and head to Britain, travel south to north
2nd half till end July - fly to Scandinavia(and start my Eurail Pass)
1st half of August - towards the Balkans
2nd half of August - Poland and westward along Germany to Holland/ Brussels.
2nd half of August to mid-September - a little south along Riveria, Switzerland, Austria to Hungary
2nd half of September to mid-October - Bucharest westard to Croatia, Italy to Athens(Eurail Pass ends)
After that, Greek Islands and fly back north to a Scandinavia City for my flight back to Asia.

This way I think my hottest time will be Switzerland(intended 8 to 10 days there) but I will minimise them by doing train journeys or hiking in the Alps north of Lauterbrunnen most of the time. Hopefully when I reach Italy by late September, it will not be hot, any ideas.

Thank you again.

May is one of my favorite months because I don't like it to be too hot when traveling either. It's usually late enough to have warmed up without getting to the really hot weather.

July/August is the best time to be in Scandinavia. It's the best time of the year and it would be unusual to be particularly hot. We were in Copenhagen in late July and early August in a room without air conditioning. It was only a problem if we left the curtains open (and windows closed) to the sun in our room. As long as we opened the courtyard window to let the cool in at night, then drew the blackout curtains to keep the sun out during the day, it was fine. Outside it was warm, not hot.

As for hiking in the Alps, even June can be a little early for the trails to be reliably open. Generally by June some trails will be open but the highest ones may not be depending on the winter and how warm of spring they are having.