The year in the Canaries, month by month
The figures come from the Santa Cruz de Tenerife observatory, 1991–2020 series: 219.7 millimetres a year over 56.4 days and an annual average of 21.7 degrees. Since temperature barely changes, the scoring crosses rain, humidity, sea temperature and crowds.
The eternal-spring label is repeated so often that it has stopped meaning anything. It is worth translating into numbers, because the number is stranger than the label.
01 Seven and a half degrees
The 1991–2020 series from the Santa Cruz de Tenerife observatory gives a monthly average temperature running from 18.3 degrees in January to 25.8 in August. The full annual range is 7.5 degrees.
To grasp how exceptional that figure is, compare it with the daily swing at the same place. In January, between the average high and the average low there are 5.6 degrees; in July, 7.3; in August, 7.0.
In other words: going from January to August means almost exactly the same jump in temperature as going from midday to dawn on any July day. The whole year fits inside one day.
And there are no extremes to offset that average. January's average low is 15.5 degrees and August's average high 29.3. Almost all life in the archipelago at sea level happens between those two values.
Seven and a half degrees between the coldest and warmest month; seven point three between midday and dawn in July.
02 Why the thermometer does not move
The cause is not latitude, although that helps. It is the water. The archipelago is surrounded by an ocean whose temperature changes slowly, and the cold Canary current, running down the African coast, cools the summer as much as the sea warms the winter.
The second factor is the trade wind, a north-easterly that blows very steadily for much of the year and sweeps away hot air before it can build up over the islands. Between sea and wind, the thermometer is left with no room to move.
The practical consequence is that here you do not choose the month for temperature. It makes no difference: in January there are highs of 21.1 degrees and in October 26.6, and neither figure prevents you doing anything.
03 The rain, which does have a calendar
If temperature does not tell the months apart, rain does. Santa Cruz de Tenerife receives 219.7 millimetres a year over 56.4 days, and that amount is very unevenly spread: 172.9 millimetres, 79 per cent, fall between November and March.
Summer is simply dry. In July 0.1 millimetres fall over 0.2 days and in June 0.6 over 0.8. That is not little rain: it is practically none, three months running.
And the eastern figures are lower still. The Gran Canaria airport station records 134.1 millimetres a year over 42.6 days, semi-desert values. On Lanzarote, traditional farming was solved without irrigation: hollows dug into volcanic ash that capture dew, and stone walls that break the wind.
04 The calima, the factor that breaks the rule
There is one phenomenon that ignores all of the above, and it is the only thing capable of pushing the thermometer out of its range. When the wind turns easterly and brings continental African air loaded with suspended dust, what the islands call a calima occurs.
The effect is twofold: temperature jumps and visibility drops. The absolute records of the two capitals show it: 42.6 degrees in Santa Cruz de Tenerife and 44.2 at Gran Canaria airport, both recorded in July.
Compared with July's average highs of 28.8 degrees, those records are fourteen and fifteen degrees above. It is the only moment when the Canary climate stops being predictable.
A calima can happen at any time of year, though it is more frequent in summer and in late winter. You cannot plan around it, but it is worth knowing that it exists and that it lasts days, not weeks.
05 And the correction the table does not show
All the figures above come from coastal stations, and on these islands that is half the story. The trade wind forms a layer of low cloud that leans on the northern flank, normally between 700 and 1,500 metres, and above it the air is dry and clear.
That means that on the same day, on the same island, there can be thick fog in the north at 800 metres, sun on the south coast and transparent air on the summit. The choice is not only of month: it is of altitude and of flank.
And it brings a practical warning. Above 2,000 metres, on Tenerife or La Palma, temperatures have nothing to do with those on the beach: it freezes in winter and the sun is far stronger all year round.
06 How to choose the month
If the criterion is weather, September and October. They are the months with the warmest sea of the year, with highs of 28.2 and 26.6 degrees, only 4.5 and 24.4 millimetres of rain and without the summer crowds.
If the criterion is walking, April, May and June. Rain drops from 10.3 to 0.6 millimetres, humidity stays below 61 per cent and highs do not exceed 26.6 degrees: the most comfortable stretch for ravines and summits.
And if the criterion is escaping the continental winter, any month will do, which is exactly the point of this article's figures. The only thing to accept between November and March is that 79 per cent of the annual rain falls in that stretch, and that half a continent has also chosen December and January.
The year's four stretches
172.9 of the year's 219.7 millimetres fall in these five months, 79 per cent, over 38.7 of the year's 56.4 rainy days. Averages of 18.3 to 21.4 degrees: it is never cold, but the sky closes over.
Rain falls from 10.3 to 0.6 millimetres and rainy days from 5.1 to 0.8. Highs of 23.0 to 26.6 degrees, humidity below 61 per cent and still without the summer crowds.
0.1 and 3.5 millimetres of rain and highs of 28.8 and 29.3 degrees. The weather is good; the problem is that it coincides with peak crowds, peak prices and the highest calima risk.
4.5 and 24.4 millimetres over 2.2 and 6.0 days, with highs of 28.2 and 26.6 degrees and lows that do not drop below 20.6. The sea is at its warmest of the year and high season is over.
