The temperatures which are quoted in daily weather forecasts are for MAXIMUM temperatures. So, for example, a weather forecast in the UK which predicts 25C means that the temperature will be that high for a short while just after lunchtime. Whereas the AVERAGE daily temperature is assessed over a 24 hour period and might only be around be around 15C on the same day (because it might only be 8C overnight)
In the Canaries the differences between day and night temperatures aren't as marked as they are in the UK but looking at 'average temperatures' (over 24 hour periods) will still give you a lower figure than what a weather forecast would predict as the maximum temperature. Daytime 'weather forecast' temperatures, are actually around 24C for much of June:
http://www.holiday-we...anaria/averages/june/
Chris