Well Tony I have heard it has been a bit iffy over the last few years, but not to worry...by the time you have run up and down Cariac Hill and quenched your thirst at the Irish Viking a few times you'll be past caring!!;)
Seriously, have a look at
http://www.wunderground.com and key in Lanzarote. Then go to History and Almanac and feed in dates and years and you'll be told what the temp and conditions were - there's even graphics on the monthly stats!! You'll be kept quiet and thirsty for ages!!!:D