If it's raining in the morning, get your sunscreen ready for the afternoon. It's less of a saying and more of a universally held truth for the weather in Wales. Wait awhile, and whatever the weather's doing now will change, often in the shortest time, leaving you to think, "When did that happen?"
Your weather will depend on where you stay in Wales. Visitors to Anglesey can expect less than half the amount of rain we get here in Llanberis at the foot of the mountains, just 30 minutes away. It can be 10 degrees hotter in the Vale of Clwyd compared to the Llyn Peninsula. And don't believe the notion that England always gets better weather than Wales - read on to understand why nearby Porthmadog, a town facing Cardigan Bay and the Atlantic Ocean beyond, can be the hottest, sunniest place in the UK.
IT'S ALL ABOUT THE ATLANTIC
Wales is no different to any other place in the UK, in that our climate is most strongly influenced by the Atlantic, it's Gulf Stream, and the Jet Stream high above it. Ours is a maritime climate, where the prevailing weather is changeable, often cloudy, often humid but rarely very cold. If you only had one weather symbol you could pin on a weather map of Wales, it would be sun-and-showers.
Generally, the only extreme weather you'll likely experience in Wales is rainfall. Capel Curig, whose weather station marks the epicentre of Snowdonia's tallest mountains, receives more than 1 metre of rain every year. In Rhosneigr on Anglesey, that amount drops to 340mm. The prevailing Atlantic winds bring moisture and the mountainous terrain of Wales is where vapour condenses and dumps plenty of the wet stuff.
But with rain comes Wales' second 'extreme' weather scenario - wind. It's a rare day indeed where there's no breeze at all. The good news is that the wind carries the weather on pretty quickly. Weather fronts cross the country, the rain sweeps away, and clear conditions follow. Each weather front often brings a change in temperature, too, alternating from warm to cold outside the summer months of June to August.
Now you see why the weather in Wales is usually changeable!
PERFECT TEMPERATURES FOR OUTDOOR FUN
Wales has a natural environment that lends itself to outdoor activities. The weather plays its part, too. Fresh rainfall keeps rivers and lakes filled, so kayaking, gorge-walking and wild swimming are typically possible through the summer period. The landscape remains green and lush, even while parts of eastern England can be parched by drought.
Temperatures are rarely too hot or too cold to be outdoors. Even on the most bracing of winter days, walks along the beach or in the mountains are possible. Thick snow cover is becoming rare, especially at lower levels, but north-facing cwms (steep-sided hollows) in Snowdonia still collect significant ice and snow through January and February. Ice-climbing is a specialist and demanding hobby practised here (Sir Edmund Hillary's team trained here for their world-first ascent of Everest). Snow is most likely to hang around on the windswept summits of the Carneddau mountains anytime from November through to March or April. Generally, though, Wales is not a snow-sports destination.
What about the summer? The record high temperature for Wales is 35.2C, recorded at Hawarden Bridge in North East Wales in August 1990. Temperatures in the 30s rarely last for more than a few days, however. High 20s are more prevalent inland, while low 20s or high teens are found at the coast. When people are stifled in London and the South East, the weather on the Welsh coast is extremely pleasant in comparison. Sea-breezes take the edge off the temperature and humidity, and again make activities more bearable. It's worth bearing in mind that UV levels can still be very high - don't think that because you're not too hot that you are not getting sunburnt.
SO WHAT IS IT ABOUT PORTHMADOG?
When the prevailing south-westerly winds are bringing the weather from the Atlantic, it's changeable here in Wales. Often cloudy, frequently showery, but not without pleasant sunshine between. Sometime, though, high pressure in the summer and winter months can swing the wind round to the east. That changes things.
In winter, high pressure that draws easterly winds from Europe or the North Sea can plunge the temperatures in the East of England and leave them stuck under grey or damp skies for days. Further west in Wales, and especially towards the coast beyond Snowdonia and the Cambrian mountains, we're shielded from those cold winds. Days can be crisp and clear, with long spells of sunshine. In autumn this can give rise to early morning mists and fog, and ground frost. The colours this lends to the Welsh landscape is magical.
Porthmadog, the Llyn Peninsula, Anglesey and the Harlech coasts are most protected from the mountains, and most likely to enjoy these conditions. Another 'clear spot' can be found in the Vale of Clwyd further east, where the Clwydian Hills form a similar barrier.
In summer, a similar pattern occurs. Easterly winds around high pressure bring settled conditions to the UK, but the cool North Sea can cause cloud and cooler temperatures further east. The higher temperatures last longer in the west, especially behind the mountains. This is when Porthmadog (and down the coast in Llanbedr where the Met Office has a weather station) can often be the warmest and sunniest place in the UK.
THE FÖHN EFFECT
Where there are mountains, there is the föhn effect. The term derives from the Alps and refers to a drier, warmer downward wind that forms in the lee of mountains. This frequently impacts on the weather in the Conwy Valley, the Vale of Clwyd, the coast from Llandudno to Prestatyn and down the Dee Estuary to Flint (and may impact on the Hawarden Bridge 'hotspot').
Even when it's overcast or wet west of Snowdonia, in the east it can be drier and a few degrees warmer. If you're staring out of your bedroom window at sullen skies in Llanberis, take a scenic drive through the mountains and find yourself under sunnier skies in Llanrwst or Colwyn Bay.
PACK FOR ALL WEATHERS
So as you can see, summers can be cloudy and wet as well as hot and dry, and winters can be cool and clear, or windy and rainy. There's no getting around it - you'll enjoy lots of weather in Wales! As the saying goes, there's no such thing as bad weather, just the wrong clothing, so bring clothes for all eventualities.
A light waterproof in summer is essential, while in winter you'll want something thicker and warmer too. Some summers suit winter-season boots while others you can get away with robust walking trainers. No matter when you come, having layers of clothes is the best approach for being outdoors. Peel off and add on as you need. Always bring sunscreen (even spring and autumn sunshine can be strong), though insect repellant is optional - bring some anyway if you're someone who attracts the little blighters. Thankfully, Wales doesn't suffer the same midge infestations as western Scotland.
MAKE SENSE OF THE FORECAST
The Met Office provides weather forecasts for Wales. It now includes a handy rain radar, too. If the winds are blowing from the west, look to the Irish Sea, St George's Channel and Ireland for what's coming.
MWIS is a specialist weather service for mountainous areas, including Snowdonia. Here you'll find specifics that relate to altitude, including wind speeds, cloud levels and windchill factor. This goes above and beyond the more generalist information from the Met Office.
For thunderstorm fans (or you're planning to avoid them if hiking in open ground), Lightning Maps is a fun, virtually-real-time record of lightning strikes. Storms are most common in late spring and early summer in Wales, and they tend to track from south to north, usually carried on hot and humid southerly winds.
Fickle at the best of times, the weather is part of the fun when you visit Wales. Umbrellas in the morning, sunscreen in the afternoon... ever wondered why? Let us tell you! Finally, don't take the weather forecast at complete face value. It's true forecasts have become more accurate in recent years, but without wanting to hit on the weather experts, our weather is so fickle that it's often easier for them to generalise.
Also be wary of exact timing. If there's a front heading from the west, plan for it to hit the Welsh coast at least an hour before the official forecast tells you. Equally, the rain can pass through faster than they sometimes predict, so get ready to go if you're waiting for the weather to clear up. Trust us - we're speaking from experience!