Management  of Type 2 diabetes mellitus (T2DM) is essential to reduce the associated adverse outcomes.  Hemoglobin A1c (HbA1c) provides an estimate of glycemia over a period from one to three months. HbA1c is recommended as a standard of care for monitoring and testing diabetes, especially among T2DM. However, HbA1c can be affected by various factors such as weather. This review aims to identify the impact of climate on HbA1c levels in patients with T2DM by reviewing the related original articles. Scientific databases were examined to search for related studies and use various related terms. The searching process wasn't limited to a definite publication year. The original included studies focused on T2DM patients, reporting levels of HbA1c in different seasons, and written in the English language. Based on the inclusion criteria, six studies were included with a total number of 12899 T2DM patients. The age range of patients was 20-90 years. Climate has a significant impact on HbA1c levels, and such levels vary between different seasons. However, it is not possible to determine the season that recorded the optimum values or reduced values of HbA1c due to the great heterogeneity across the studies.