Climate change is rewriting the rulebook for trip planning – and travellers need to adapt.

I spent April and May this year travelling across Nepal – prime trekking season and often billed as the "best time to visit". Almost every online guide promised clear skies and comfortable temperatures. Instead, I found hazy polluted air and low visibility, especially at lower elevations. Early monsoons swept across the country, briefly clearing the smoke but replacing it with downpours I hadn't prepared for. The gap between expectation and reality was jarring.

This isn't just a Nepal problem; travel is facing climate-driven disruptions everywhere. Australia recorded its hottest March on record this year, with temperatures 2.41C above the historical average. In Japan, cherry blossoms are blooming earlier than ever. Across the globe, longer summers, shorter winters and erratic "false springs" are now routine.

"The planet's warming since around 1980 is making heatwaves, droughts and floods more frequent and severe," says Jonathan Erdman, senior meteorologist at The Weather Company's weather.com. "All three of these are most common during summer, when travel peaks."

But the unpredictability now stretches year-round. "Extremely wet and dry periods can happen any time of year – including shoulder season – if the weather pattern gets stuck for a while," Erdman adds.

Traditionally, "best time to visit" meant peak travel season: a sweet spot of good weather and easy access to experiences. Over time, the advice became more tailored. An Italy travel guide might now suggest April and October for fewer crowds, February for Venice Carnival or January for skiing in the Dolomites – timeframes that cater to more specific experiences beyond just "good weather".

But despite these refinements, the assumption lingers that seasons will continue to behave as they always have. That Dolomites ski guide probably won't mention that snowfall across Europe has been unreliable.

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Juliana Shrestha, co-founder of Duluwa Outdoors, a female-led Nepal-based company that curates educational experiences in the outdoors, says this inconsistency is one of their biggest challenges. "Earlier, when clients asked for a snow trek in December, we could suggest options like Annapurna Base Camp," Shrestha says. "But now, it's harder to say confidently whether conditions will be right. We just don't know anymore."

That line – we just don't know anymore – feels far too familiar. It creeps up in my travels, in conversations with local guides and increasingly in academic studies. Stanford researchers, for instance, have found that........

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