Calima in the Canary Islands: what to do when the sky turns yellow
You get up, open the blind and Teide is not there. The sky has an odd colour, somewhere between orange and dirty, there is a film of fine dust on the car and the air smells dry. That is the calima, the Saharan dust haze that settles over the islands, and the first thing worth knowing is that it is not a rarity: between 2010 and 2017 AEMET identified 123 episodes and 574 days with Saharan dust across the archipelago, around 20 per cent of all days.
What almost nobody covers is the other half: what you do on that day. Whether you go out walking, whether you take the child to the park, whether tomorrow's flight is a worry, whether closing the windows helps at all. That is what this guide is about.
When it arrives, and the detail almost nobody knows
There is no single season, and that is the first misunderstanding. According to the AEMET study, summer episodes are the longest (six days on average, with a record of twenty in 2013), while winter ones are the most intense: every episode that has passed 100 micrograms per cubic metre occurred between December and March.
And here is the practical detail that changes the decision you make that morning:
Did you know? The dust does not arrive at the same altitude in every season. AEMET sums it up like this: in summer the intrusions tend to affect the high ground of the archipelago, while in winter they tend to affect the low ground. Put another way, in August the calima can be ruining the view at the summit while down on the coast you barely notice it, and in February it can be exactly the other way round.
If what matters to you is visibility, the pattern is narrower still. At Gran Canaria airport, between 1998 and 2011, visibility dropped below five kilometres because of dust above all in February (2.8% of days) and March (2.2%), and in May and June it did not happen once in fourteen years.
Be careful with the figures going around, because they measure different things and are all true at the same time: some 72 days a year with detectable dust, between 33 and 65 days a year at one particular station in Tenerife, and only one to three times a year for the strongest episodes. "There is calima" and "you cannot see the next island" are not the same statement.
The warnings do not all say the same thing, and it pays to know which one you are reading
There is a widespread confusion here. Phrases like "red alert for calima" circulate, and they do not match how the system actually works. Three separate systems are in play, and Spanish keeps them apart with words that would all collapse into "warning" in English, so the originals are worth holding on to.
AEMET, the national weather agency, works with the aviso, the meteorological warning, and for suspended dust it contemplates only the yellow level. The national plan puts it in a single sentence: when a warning is considered appropriate, the yellow level will be assigned, normally with visibility below 3,000 metres. There is no orange or red AEMET aviso for dust. And the criterion is visibility, not concentration.
The Gobierno de Canarias is another matter. Within its emergency plan it declares prealerta (pre-alert), alerta (alert) or alerta máxima (maximum alert), and it is that declaration which can lead to actual measures. Under prealerta there is considered to be no risk to the general population, though there may be to some specific activity, and no advice is issued to the public. Under alerta, self-protection advice is issued. Alerta máxima even allows activities to be suspended.
In practice the Canarian declarations talk about concentration, not visibility. The prealerta of February 2026 quoted values of 50 to 200 micrograms per cubic metre, with the densest layer above 400 or 500 metres of altitude. The alerta of December 2022 spoke of 500 to 2,000 micrograms and visibility below 1,500 metres. This needs saying precisely: those numbers come from the published declarations, not from an official table of thresholds, because the numerical annex of the plan is not available openly.
There is also a third route, that of air quality, with its own index and its own thresholds. It is not the same thing as the meteorological aviso, nor as the emergency alerta, and that is why you can see a day with no yellow aviso and the index in red.
How to find out how much dust there is right now
This is the most useful part of the whole article and almost nobody uses it: the Canaries have a public air quality network with data by station, updated every half hour.
- Live data by station: the Red de Control y Vigilancia de la Calidad del Aire of the Gobierno de Canarias
- Active exceedances, to see at a glance where the limit is being passed
- The air quality index (ICA), which translates micrograms into categories
The index categories for PM10 run from good (0 to 20) to extremely unfavourable (from 151 upwards). Two caveats that appear nowhere obvious and change how you read the number. The first: the index uses a rolling average of the last 24 hours, so it lags behind what you notice out in the street. The second: values above the maximum of the worst category are discarded as presumed errors, so in a very strong episode the real figure can end up outside the index altogether.
To know whether it is building or easing, AEMET publishes surface dust concentration probability maps with a domain of their own for the Canaries, with thresholds of 50, 100, 200 and 500 micrograms and forecasts at one and two days.
Who should take care, and what to do
The official recommendations from Sanidad, the health department of the Gobierno de Canarias, list as most sensitive children, older people, people with chronic respiratory illnesses such as asthma or bronchitis, people with cardiovascular disease, pregnant women, outdoor workers and smokers.
What the official guidance says, without embellishment:
- Keep doors and windows closed and avoid going out if there is a chronic respiratory illness
- Do no intense physical exercise while the situation lasts
- Keep the usual medication to hand and stick to the plan you already have
- Drink more fluid, because the dust dries out the airways
- Wipe dust away with a damp cloth, never dry
- If you are driving, put your lights on and slow down
Two facts that are almost never mentioned and that genuinely matter. The first: the effect does not end when the dust leaves. Sanidad warns that chest discomfort, coughing, palpitations or a greater susceptibility to infection can last for at least the five days following the start of the episode. The second: if you get worse, the official instruction is to go to your health centre, not to hospital A&E. For questions there is the information line 012, and for a genuine emergency, 1-1-2.
On face masks there is no official recommendation, Canarian or national, neither for nor against, so you will not find a specific type recommended here.
Planes and schools: what actually stops
The reference episode is that of February 2020, and it remains the worst in the forty-year series in terms of loss of visibility. The eight Canarian airports and the airspace of the archipelago closed for a few hours on 23 February, for the first time in history. Between the 22nd and the 23rd some 1,000 flights and around 120,000 people were affected, with 745 cancellations and 84 diversions on the Sunday alone. Visibility fell as low as 400 metres in Gran Canaria, and at Tenerife Sur it stayed below 500 for two and a half hours.
That said, there is no published threshold of visibility beyond which a flight is cancelled or diverted: it is an operational decision that depends on the airport and on the aircraft. If you are flying in the middle of an episode, the reliable information is your airline's and the airport's, not a general rule.
With schools something similar happens. The Canaries have a protocol for suspending classes because of adverse weather, with three levels going as far as a total suspension including canteen and transport, but calima is not named in the list of phenomena it covers. In February 2020 classes were indeed suspended on every island for wind and calima, as a one-off decision. In other words: it can happen, but there is no automatic rule you can look up in advance.
Why "the legal limit has been exceeded" does not mean what it sounds like
Every so often the news appears that some town has exceeded the legal limit for particulates because of the calima, and behind it comes the logical question: so why is nothing being done.
The answer is in the regulation. Spanish air quality legislation establishes that exceedances attributable to natural sources, and Saharan dust is one, are not counted as exceedances for legal purposes and do not oblige anyone to set action plans in motion. There is an official methodology for discounting them and an annual list of natural episodes.
It is not an accounting trick: it separates what you breathe from what the administration can actually correct. A traffic plan does not shrink the Sahara. But it does explain why a figure that sounds alarming triggers no measure at all.
And in the meantime, what
An episode lasts 4.7 days on average, though the summer ones run longer. AEMET itself admits how hard it is to predict the intensity, the duration and the areas affected, and adds a detail worth keeping in mind: the visibility minimums do not coincide geographically with the PM10 maximums. Seeing clearly does not mean the air is clean, and the other way round holds too.
If the plan for the day falls apart, we have a list of indoor alternatives in What to Do in Tenerife When It Rains: Plans to Save Your Day, and it works just as well for a dusty day. And if you want to understand the rest of the islands' weather picture, here is our full guide: The Islands of Eternal Spring? The Complete Guide to the Weather in the Canary Islands.
Sources
1. AEMET, Nota Técnica 35, "Caracterización de las intrusiones de polvo en Canarias", 2021.
2. AEMET, "Catálogo-guía de fenómenos meteorológicos adversos que afectan a Gran Canaria", 2018.
3. AEMET, Plan Meteoalerta, annex of thresholds and warning levels, 31/05/2022.
4. Decreto 18/2014, PEFMA, BOC nº 70 of 09/04/2014, and the prealerta (15/02/2026) and alerta (25/12/2022) declarations of the Dirección General de Seguridad y Emergencias.
5. Gobierno de Canarias, Red de Control y Vigilancia de la Calidad del Aire, and Orden TEC/351/2019 on the Índice Nacional de Calidad del Aire.
6. Real Decreto 102/2011 on the improvement of air quality, article 22 and annex XIV.
7. Gobierno de Canarias, Dirección General de Emergencias, self-protection advice for calima.
8. Gobierno de Canarias, Dirección General de Salud Pública, recommendations for calima episodes (16/04/2026 and 16/02/2021).
9. WMO GAW Report No. 259, "Desert Dust Outbreak in the Canary Islands (February 2020)", AEMET and WMO.
10. Gobierno de Canarias, protocol for information and monitoring of adverse weather phenomena in the education system.
