Normally the northern side of Tenerife is bathed in fog, and the southern side has abundant sunshine. The island is only about 60 miles long and (sometimes much less than) 20 miles wide. Along with a 12,198 ft. volcano in the middle, this makes for quite a lot of ecosystems mashed together! This means you can feel hot desert winds blow across cactus in the morning, and be cooling off in a rainforest fog in the afternoon, with time in the middle for some sunbathing on the beach!
Hike #6 from the Tenerife Rother Walking Guide, Barranco Madre del Agua (4 miles)
On our first morning in Tenerife, there were high clouds obscuring the sun and limiting it to a dim yellow ball in the sky, so we figured this might be a good day to get a hike in on the north side while the fog wouldn't be forming. Of course the haze limited the visibility as well, but at least it wasn't as dense! From our hotel in Los Cristianos, we drove the winding road up and over the Teide crater, and then a long way down the other side. I love this drive because it winds through forest of pine trees with impressive viewpoints (not to mention the crater itself with views of Teide), and we were excited because finally we would get to hike as well as drive through the forests.