Non-zero dispersion fiber (NZDF) ribbon cable has become an important alternative for long-haul high-speed network constructions. Since such networks require low polarization mode dispersion (PMD), it is very important to know the PMD performance of NZDF ribbon cables under different structural and environmental conditions. In particular, the ambient temperature can vary rapidly and randomly during the operation. This can cause high PMD variations in optical fiber cables. Therefore, effects of ambient temperature change on PMD should be analyzed for viability of the high-bit rate communication. In this paper, experimental results about effects of ambient temperature change on PMD characteristics of slotted core NZDF ribbon cables have been reported. Furthermore, variation of the transmission distance due to PMD variations caused by ambient temperature change has been analyzed. The ambient temperature has been changed between 10 degrees C and 60 degrees C during experiments. Measurements have been performed on two different rings formed by splicing fibers of a NZDF ribbon cable. The first ring has been formed by splicing all lateral fibers, i.e. the first and the last fibers of all 4-fiber ribbons in the cable. The second ring has been formed by splicing all central fibers, i.e. the two fibers in the center of all 4-fiber ribbons in the cable. Results exhibit a 14.2 % PMD variation with ambient temperature change for the first ring while they show a 10.7 % PMD variation for the second ring. Using experimental results it has been computed that ambient temperature change degrades maximum transmission distance of the first ring by 23.3 % and that of the second ring by 18.5 %. To simulate effects of actual field conditions on PMD variations, the NZDF ribbon cable has been exposed to ambient temperature variations from 12 degrees C to 26 degrees C for 48 hours in the field. PMD variation with ambient temperature change has been determined as 13,4 % and it has been computed that ambient temperature change degrades maximum transmission distance by 22,2 %. Experimental results reported in this paper obviously show that ambient temperature change significantly affects PMD performances of NZDF ribbons and degrades maximum transmission distances in these cables.