Seasonal variations on the milk composition have been well documented. New Zealand (NZ) is one of the key global dairy products processors; however, the detailed information about seasonal variation of NZ milk is not available to the public. As the dairy cows are pasture fed in NZ, the composition and physicochemical properties of NZ milk may be significantly altered through the weather cycle. In the current research, we demonstrated how milk composition and properties are altered through 10-mo time and if such changes have a significant impact on the heat stability of the skim milk or not. Bovine milk samples were provided by 3 dairy herds, from no less than 1000 cows, in NZ. The samples were collected 2 times a month across the 4 seasons. The principal components analysis (PCA) showed winter is a transitional period that separates the autumn milk (AM) from the milk yielded in spring and summer in terms of composition. The milk collected in autumn and early winter had significantly higher protein, fat and total solid contents. The AM associated with lower pH, a higher level of free Ca²⁺, higher ethanol stability, and higher sedimentation rate induced by centrifugation. Regarding detailed lipid composition, AM is enriched in short-chain fatty acid, conjugated linoleic acids (CLA), and phospholipid (PL). In batch heat treatment experiment (85°C/5min), it showed that skimmed AM is more heat stable than spring and summer milk. Moreover, the skim milk heat stability is strongly correlated with ethanol stability of the raw full-fat milk (Pearson correlation, P < 0.05). The obtained results provided detailed insights of seasonal variations of NZ’s milk. The enriched short-chain fatty acids in AM suggested that the AM derived butter or anhydrous milk fat products may have relatively softer texture. As short-chain fatty acids are relatively easier absorbed into the body and are metabolized rapidly in the liver. Also, considering the health benefits associated with the CLA and the milk PL, AM could be preferably used for manufacturing nutritional ingredients.