When the ambient temperatures are lower, the blocks should be protected from wetting. The heat capacity of a wet block is very high. If the temperature drops in the night, the next day – despite the air temperature being above 5°C – the block temperature can be lower, which may affect bonding with the mortar.
On the other hand, in the summer, it is even recommended to moisten the blocks in order to prevent from rapid absorption of water contained in the mortar. Of course, the block may not be soaked, but just moistened. A block, when soaked, may slide on the wall.