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 sleightly shrink. As the stucco shrinks the small cracks may start to appear. Environmental factors can increase the likelyness of check cracking. In hot dry weather a light spray(mist) of clean water is recommended, and may help reduce the apprearance of check cracking.
Why do small cracks appear in stucco finishes?