My favourite time of year to visit the Canary Islands e.g. Lanzarote, is October. Around this time it's usually about 27 degrees celsius. This is a lovely temperature; plenty of heat but not suffocating so you can still get out and about. It's a nicer time of year to visit as it's not as hectic as July/August. If you go at the other end of the year like March, you may find it too cool. It would typcially be about 23 degrees celsius.