How to Compare Weather Before You Book a Trip

Weather Explained

When you’re booking a trip two or three months out, the forecast is useless — no one can tell you whether it’ll rain on a specific day that far ahead. But that doesn’t mean you’re flying blind. Climate averages, built from decades of records, tell you what each destination is typically like at that time of year. The skill is knowing how to read and compare them. Here’s how to do it properly.

In How Accurate Is a Weather Forecast? we explained why long-range forecasts fall apart beyond about a week, and why climate averages are the right tool for planning ahead. This guide is the practical next step: how to actually compare those averages between destinations and turn them into a confident booking decision. The method is the same whether you’re choosing between countries, islands, or months — once you know which numbers matter and how to weigh them. Here’s how to compare weather before booking, step by step.

The Five Numbers That Actually Matter

Most weather pages throw a dozen figures at you. For deciding when and where to travel, only five really matter. Learn to read these and you can size up any destination in under a minute.

• Average high temperature — the daytime warmth you’ll actually feel. More useful than the “average temperature,” which is dragged down by overnight lows you’ll mostly sleep through.
• Sea temperature — the make-or-break number for a beach trip. Air at 25°C means little if the sea is a bracing 17°C. Anything from about 22°C upwards is comfortable for most swimmers.
• Rain days — the number of days per month with meaningful rain. Far more useful than total millimetres, which one freak storm can distort. Rain days tell you how often you’ll actually be affected.
• Humidity — how oppressive the heat feels. 30°C in dry air is pleasant; 30°C at 80% humidity is exhausting. It’s the gap between the temperature and how the day actually feels.
• Daylight hours — easy to forget, but it shapes how much you can fit in. A June evening that stays light until 9pm is a very different trip from an October day that’s dark by 6.

Weigh Them for Your Kind of Trip

Here’s the part most people skip: the five numbers don’t matter equally — their importance depends entirely on what you’re going to do. The same destination can be perfect for one traveller and wrong for another in the same week.

So a beach traveller and a hiker looking at the same island in the same month should reach different conclusions — because they’re reading different numbers. That’s the whole skill: not “what’s the weather,” but “what’s the weather for what I’m doing.”

Read the Averages Critically

Averages are powerful, but they hide things. Three habits keep you from being misled:

• An average is not a guarantee. A month that averages two rain days can still hand you a freak storm on the day you arrive. Averages tell you the odds, not the outcome — book around the likely, but pack for the possible.
• Some months barely differ. On most Mediterranean destinations, July and August are nearly identical — same heat, same dry skies, same warm sea. Agonising over which of two peak months to pick is wasted effort; the real decision is almost always peak season versus shoulder season, not which peak month.
• Shoulder seasons are more variable. The further you move from mid-summer, the wider the range of what you might get. May and October are wonderful on average, but a single average figure hides a bigger spread of good and bad days than July does.

The Method in Action: Three Greek Islands, Two Months

Let’s put it to work. Say you’re choosing between three Greek islands — Santorini, Crete, and Corfu — and you’re weighing peak summer (July) against the shoulder season (September). Here’s how they compare on the numbers that matter.

What the numbers tell you. In July, all three are hot, bone-dry, and have an almost identically warm sea (24–25°C) — on weather alone they’re nearly interchangeable, so you’d choose on character rather than climate (Santorini for the caldera views, Crete for adventure and beaches, Corfu for its green Ionian landscape). The interesting story is September: Santorini and Crete stay nearly as dry as in summer, with the sea still summer-warm — arguably better than July once you factor in thinner crowds and lower prices. Corfu tells a different story — its rain days jump to seven or eight, because as an Ionian island it gets far more autumn rain than the dry Cyclades. The sea’s still warm, but September carries a real chance of washed-out days.

So the decision falls out naturally. For a September beach trip, Santorini or Crete is the safer bet — warm sea, dry skies, fewer crowds. For July, all three deliver the same weather, so pick on the kind of trip you want. And if Corfu’s the dream, lean toward July or very early September, before the autumn rains build. That’s the method: the numbers don’t choose for you, but they turn a vague “which one?” into a clear, defensible decision.

The Same Method Works Anywhere

Nothing here is specific to Greece. Whether you’re weighing the Algarve against the Amalfi Coast, or deciding between May and October for a single destination, the process is identical: pull the five numbers, weight them for your kind of trip, read the averages critically, and let the comparison do the work.

One caution when you widen the net: compare specific places, not whole countries. “What’s the weather in Italy in June?” has no useful answer — the Alps and Sicily are different worlds. The same is true of Spain, Portugal, or anywhere with varied geography. Once you’ve narrowed to a region or city, check that place’s averages, because national figures blur exactly the differences you’re trying to decide between.

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Sources

• World Meteorological Organization — climate normals and standards (wmo.int)
• Climates to Travel — Mediterranean and Greek island climate data (climatestotravel.com)
• Weather Atlas — Corfu, Crete and Santorini monthly averages (weather-atlas.com)
• Greeka — Greek island weather by month (greeka.com)

WorldWeatherTime provides climate averages, sea temperature and live conditions for cities worldwide. Search any destination to compare your options and book smarter around the weather.