The weather can have a huge influence on the success of a trip. Dealing with freezing temperatures, heat waves, wind, rain, snow or thunderstorms, all offer their own dangers.
With a little knowledge and some practice it’s possible to become reasonably successful at predicting the weather up to a few hours in advance.
But before you try and work out whether that cloud coming towards you is going to unleash a hailstorm or benignly pass you by, it pays to do some research beforehand on the likely weather you’ll encounter over the course of your trip.
This allows you make informed equipment choices such as packing a warmer sleeping bag or bringing a sun hat.
You might find that you need to change the date of your trip or allow some extra days in case you have to sit out some particularly bad weather.
The type of trip that you’re taking will also make a difference. The wind won’t be too much of an issue on a low level hiking trip, other than watching for falling branches. Factor in a canoeing journey on a large, open lake system and a strong wind could see you shorebound until it passes.
Sources of weather information
Getting weather information shouldn’t be an issue in this day and age. Science and technology move on at an alarming rate and with it so does our ability to access accurate forecasts.
Research the climate
At the very least you should familiarise yourself with the climate of the area that you’ll be travelling through. If your trip is close to home then you probably already have a good idea what temperatures to expect in summer compared to autumn.
If you’re travelling abroad then you might need to do a bit more research. WeatherOnline is an excellent source of climate information. You can search for a country or narrow it down to a particular region.
An example of a climate temperature graph. This will give you a guide to the likely temperature range for the area that you’re visiting. Source: WeatherOnline
It will give you the average temperatures and rainfall by month as well as an overview of the general climate and what weather you can expect at different times of the year. You’ll even get some suggestions on the types of clothing to bring.
You can usually get similar information from travel guides such as Lonely Planet which can also serve as an excellent source of inspiration for future trips. I’ll often pick up a travel guide before taking a trip in a country I’ve not been to before.
Long range forecasts
You can start to narrow down your research using long range forecasts. They won’t tell you what the weather will be on a particular day but they can give a good indication of any big shifts in weather patterns usually up to a month in advance.
The accuracy of long range forecasts depends on the country. In the UK it can be incredibly difficult to predict the weather accurately more than a few days in advance as it changes rapidly.
In countries that have a more stable climate it’s possible to get a more accurate long range prediction. The Met Office offers the best weather information in the UK and I’ve usually found AccuWeather to be quite accurate for trips overseas.
Blogs and forums
Blogs and forums also offer some excellent information. First hand accounts from people who have travelled through a particular area at the same time of year or even on the same trail can be invaluable.
You might not experience exactly the same conditions but you should be able to get an idea of whether certain rivers will be flooded or if snow will cause a problem for travelling.
If you’re hiking a well developed trail then some have websites dedicated to giving up-to-date information on trail conditions as well as weather updates.
Getting daily forecasts can be difficult, especially in remote areas where phone signal is limited.
Downloading weather apps ahead of time is a good idea. Most will give you an accurate forecast from a day or two in advance to up to a 10 or even 14 days. It can be useful to write the information down in case you can’t access it once you’ve started your trip.
The BBC Weather App which gives a reasonably accurate forecast for anything up to 10 days in advance.
People have their own preferences about which apps are more accurate than others. Some are better for specific areas.
Again I use the AccuWeather app for use abroad but often combine it with the BBC weather app (which gets its data from the Met Office).
Proper planning can go a long way to making sure you are prepared for the types of weather to expect but there are other, natural clues that will help you predict the weather on an hour by hour basis when you’re outdoors.
The “weight” of air pushing down on Earth causes air pressure (atmospheric pressure). The density of air molecules changes depending on altitude so the higher you go, the lower the air pressure (as there is less air above pushing down).
Changes in air pressure are a good indication of changes in the weather.
When there is low pressure, the air rises as there is less “weight” bearing down on it. As the air rises, it cools in the atmosphere.
This process of cooling causes condensation to form which then releases in the form of rain. If the temperature is low enough, instead of rain you get snow or hail.
Changes in air pressure can be a good indication of changes in the weather. Falling pressure is an indication of bad weather on the way whereas rising pressure indicates good weather.
In order to identify changes in pressure the easiest way is to use a barometric altimeter. You can buy watches which have this functionality built in. Many include other features such as a digital compass which can be very useful to have.
The barometer will show you changes in atmospheric pressure. The more quickly the pressure drops or rises will indicate how dramatic the change in weather is likely to be. If you see a sudden drop then it might be a good idea to get down off that mountain or put up your shelter.
While you don’t need such a device, if you have a particular interest in weather forecasting or in keeping detailed notes about the weather you experienced on a trip, then it could be a useful tool to bring with you for a small weight penalty.
If you don’t have a barometer or portable weather station with you then there are natural clues you can use to work out changes in the weather.
If you’re having a campfire, watch how the smoke behaves. If it rises high in a vertical column then it suggests high pressure (and good weather). If it hangs low to the ground instead then it might mean that rain is on the way.
Heavy dew late in the evening or early in the morning suggests that you will have good weather the next day.
Plants can give an indication of a change in air pressure. They release gases at lower pressure especially in damp areas which gives off a compost aroma.
You might find that your sense of smell increases as pressure drops. Lower pressure causes swamps and plants to release gasses.
If you’re in a swampy or damp area and it starts to smell like compost then it’s a good indication that the weather is going to take a turn for the worse.
Flies and mosquitos swarm and bite more when a storm is on the way. Larger animals such as sheep and deer will move off of mountainsides and head for more sheltered valleys until bad weather passes.
Birds either stop flying or fly lower to the ground than usual when rain is on the way. This is a direct result of low pressure as it makes taking off more difficult, so pay attention to what the wildlife around you is doing.
Air will always want to move from areas of high pressure to areas of low pressure. As these masses of high and low pressure meet, wind is created.
While you obviously can’t see the wind, you can feel its effects. Try to be aware of any changes in wind direction or speed as these are good indicators that the weather is about to change.
Depending on how exposed or high your journey, the wind could have a big effect on your ability to travel.
Areas of low pressure spin anticlockwise (in the northern hemisphere) which is why if you watch a hurricane moving on a weather map you’ll always see it spinning anticlockwise. In the southern hemisphere it is reversed.
Wind blowing from the south or east usually precedes bad weather which is why it’s useful to remember the old adage “wind from the south brings rain in its mouth”.
A northerly or westerly wind is an indicator of fair weather so remember “wind from the west brings weather that’s best”.
Clouds are an excellent way of predicting the weather and understanding the difference between cloud types is a useful wilderness skill to have.
In order for clouds to form, water vapor rises, cools and condenses in the atmosphere. Small particles such as smoke, dust and salt are attracted to the moisture in the air and are absorbed by the water droplets. It’s these water droplets that join together to form clouds.
It’s only once these droplet become too heavy to stay suspended in the air that they fall in the form of rain or snow.
Clouds look differently depending on what is going on in the atmosphere which is how you can tell what the weather is likely to do by looking at them. Source: University of Washington
Dark, billowing clouds filling up the sky will tell you that precipitation is on the way and combined with an understanding of the wind and air pressure, you will have a useful weather forecasting system that doesn’t rely on batteries or signal.
Start to make a habit of looking at the sky when you’re out and about. Try to memorise the different cloud formations and see if you can start to predict what the weather is going to do. With practice you can start to get quite accurate.
Clouds can be categorised into four groups. There are high level, mid level, low level and vertical growth clouds.
High level clouds
High level clouds form above 6,000 metres (20,000 feet) and they are the highest forming clouds in our atmosphere. Because they are so high up they form primarily from ice crystals rather than water droplets.
There are three types of high level clouds. These are Cirrus, Cirrostratus and Cirrocumulus.
Cirrus clouds look wispy and white. Cirrus is actually latin for ‘lock of hair’ as that’s what they resemble. They often look like they’re not moving because they’re so high up but they are the fastest moving clouds.
While they are fair weather clouds they often indicate a change in weather within the next 24 hours. If you see them it could mean that bad weather is on the way.
Cirrus clouds look like wisps in the sky
Cirrostratus clouds look like a sheet covering the sky. These clouds are so thin that the sun or moon can shine through them, making it look like they have a halo around them. As with Cirrus clouds, these also indicate poor weather in the near future.
Cirrocumulus clouds appear in white puffs across the sky. They often form in lines which looks like the scales on the back of a mackerel which is why they’re referred to as ‘mackerel sky’. They usually indicate fair weather.
Mid level clouds
Mid level clouds form between 2,000 and 6,000 metres (6,500 and 20,000 feet) and often block out the light from the sun or at least make it look very hazy. They can be made up of ice crystals but are more likely to be comprised of water.
There are two types of mid level clouds. These are Altostratus and Altocumulus. Alto meaning ‘high’.
Altostratus clouds are usually grey or grey/blue in colour and cover the whole sky. Not usually rain clouds but they often indicate that a storm is on the way so get your rain jacket ready.
Altostratus clouds form between 2,000 and 6,00 metres and can indicate rain is on the way.
Altocumulus clouds tend to be more of a greyish white with one part darker than the other. They resemble large, fluffy sheets and often form in large groups covering the sky.
Low level clouds
Low level clouds form below 2,000 metres (6,500 feet) and often carry rain with them. They always block out sun and moonlight because they sit so low in the atmosphere.
There are three types of low level clouds. These are Stratus, Stratocumulus and Nimbostratus.
Stratus clouds are the most low lying and are often formed around coasts and mountains. As clouds go they’re pretty miserable. Very grey blankets that cover the sky bringing with them drizzle or light snow.
Fog is actually a very low lying stratus cloud. Stratus means ‘layer’, hence why they form in a big sheet, covering the sky.
Stratocumulus clouds look bumpy and grey. They don’t cover the whole sky but often look patchy or line up in rows. While they can bring precipitation it will never be more than a light drizzle and usually nothing at all.
Stratocumulus are generally fair weather clouds though they can bring light rain or drizzle.
Nimbostratus clouds are your standard rain cloud. Nimbo comes from the latin ‘nimbus’ which means precipitation. They form in large, grey sheets and are quite thick. If you see one of these clouds it’s just about to rain if it isn’t already raining.
Vertical growth clouds
Clouds with vertical development usually start in the low level range but can reach all the way up to the high level. You want to pay particular attention to any clouds that seem to be growing vertically as it pretty much always means bad news.
There are two types of vertical growth clouds. These are Cumulus and Cumulonimbus.
Cumulus means ‘heap’ which is how they form. They are your typical cotton-ball clouds which usually have a large, flat base and a fluffy, domed top.
They are generally fair weather clouds though if you see them before 12pm they can indicate poor weather later in the day. The saying to remember is “in the morning mountains, in the afternoon fountains”.
If you see a cumulus cloud growing vertically then it is likely to indicate a storm approaching.
The very ominous view below a cumulonimbus cloud. Stretching from less than 2,000 metres to over 6,000 metres these clouds can bring some seriously dangerous weather.
Cumulonimbus clouds are the ones to watch out for especially if you’re anywhere exposed. They grow vertically and can resemble the shape of an anvil (though you won’t be able to see the shape if it’s overhead). The anvil will point in the direction that the cloud is moving.
These clouds can bring very dangerous weather in the form of rain, hail, lightning and even tornados in some cases.
If you are interested in learning more about cloud formations then there’s an excellent PDF produced by the Met Office on how to read the sky
Looking out for the natural clues around you will give you the ability to make a pretty good prediction of the weather a few hours in advance.
You don’t have to spend your whole time checking readings and examining the clouds but as you’re moving through the environment just become aware of any changes around you, whether that be the wind direction or the clouds building up ahead.
It’s always a good idea to make checking the weather part of your pre-trip planning, even if it’s just a day hike in the hills. The weather can change rapidly and what started out a sunny day could turn nasty later on.
For longer journeys or in areas that you are unfamiliar, get any available information on the likely weather conditions before heading out. You’ll be better prepared and much more likely to have a safe and enjoyable trip.
Do you have any other ways of predicting the weather?