It's something I've been thinking about a lot since returning from our recent 17-day journey through South America.
We travelled through São Paulo, Buenos Aires, Iguazú Falls, Búzios and Rio de Janeiro, and despite carefully choosing when to travel, we experienced weather that was completely unexpected for the time of year.
And at times, it felt as though the rain was following us.
When you've travelled thousands of miles, planned your itinerary carefully and pictured yourself exploring under blue skies – or perhaps doing absolutely nothing on a beautiful Brazilian beach – persistent rain can initially feel hugely disappointing.
But somewhere along the way, something changed.
We stopped waiting for the weather we thought we should be having and started enjoying the trip we were actually having.
And strangely, some of our most memorable experiences happened because it rained.
One rainy day, instead of sitting on the beach as planned, we jumped into a taxi to go somewhere else.
On the way, we unexpectedly came across a family of capybaras.
It was one of those wonderful, completely unplanned travel moments. We hadn't gone looking for them. They weren't part of an excursion or carefully constructed itinerary. We simply happened upon them.
Had the sun been shining, we'd almost certainly have been lying on the beach – and we would never have seen them.
On another day, the weather encouraged us to explore rather than stop. We walked across a headland, discovered incredible views and found a place we probably wouldn't even have known existed if we'd spent the day exactly as originally planned.
It made me wonder: how many of the best travel experiences happen when the original plan goes wrong?
Perhaps social media hasn't helped.
We are constantly presented with an image of what the perfect holiday is supposed to look like: cloudless blue skies, turquoise seas, empty beaches and spectacular sunsets.
Reality isn't always quite so cooperative.
Weather is one of the few elements of a holiday that nobody – not your travel company, your hotel, your tour operator or even the most sophisticated weather forecast – can guarantee.
You can research historical temperatures and rainfall, choose what should statistically be the best time to travel and plan everything meticulously.
And it can still rain.
The question is what happens next.
I'm not suggesting for one moment that weather doesn't matter.
If you've booked a week specifically to lie on a beach and it rains relentlessly, of course that's disappointing. Severe weather can also affect flights, excursions and occasionally whether it is safe to travel at all.
But there's a difference between acknowledging disappointment and allowing the weather to decide whether your entire holiday has been a success.
Once we stopped looking out of the window hoping for the weather to change, we started asking a different question:
What can we do today that we wouldn't have done if the sun was shining?
That small change of mindset completely altered our experience.
Restaurants we might not have discovered. Longer lunches we might not have enjoyed. Different neighbourhoods. Unexpected walks. Conversations. Wildlife. Views. Places we hadn't planned to visit.
Travel became less about completing the itinerary we'd imagined and more about experiencing the destination that was actually in front of us.
After more than 37 years working in travel, I know how much thought people put into choosing the best time to travel. Weather understandably plays an enormous part in that decision, and good travel planning should always take seasonal conditions into account.
But our South America trip reminded me of something else.
A weather forecast can tell you whether it might rain. It can't tell you whether you're going to have an extraordinary day.
Some of our greatest pinch-me moments on this journey weren't planned at all.
And perhaps that's one of the reasons we travel in the first place.
Not simply to reproduce the perfect pictures we've already seen, but to discover something we weren't expecting.
It can change it.
It can frustrate you. It can alter your plans. And occasionally it can mean accepting that something you desperately wanted to do simply isn't going to happen.
But does it automatically have to ruin the experience?
I'm no longer convinced it does.
Sometimes Plan B becomes the story you tell when you get home.
Sometimes the rainy afternoon leads you somewhere you would never otherwise have gone.
And sometimes, while you're busy wishing the sun would come out, a family of capybaras appears at the side of the road.
Maybe there is such a thing as bad weather. But perhaps there doesn't always have to be such a thing as a bad day on holiday.
