Another term for this is check cracking. Check cracking in stucco is normal, as stucco cures the water evaporates. This evaporation process causes the stucco to slightly shrink.
As the stucco shrinks the small cracks may start to appear. Environmental factors can increase the likeliness of check cracking. In hot dry weather a light spray(mist) of clean water is recommended. And it may help reduce the appearance of check cracking.