Climate change has led to an increase in global temperatures and adversely impacted human health, for example, by exacerbating the burden of non-communicable diseases. This systematic review and meta-analyses aim to synthesize evidence on the effect of heat exposure on the morbidity and mortality associated with cardiovascular diseases, chronic respiratory diseases and diabetes mellitus in Low-and Middle-income countries (LMICs). Five databases (Medline, Embase, Web of science, Global health and Africa wide information) were initially searched using keywords related to heat, cardiovascular, respiratory disease, diabetes and LMICs to identify relevant peer-reviewed studies, published from inception to June 2024. An updated PubMed search on 29 April 2025 was done to identify additional eligible studies. Meta-analyses were conducted to quantify the pooled effects of the association between temperature and disease-related mortality/morbidity. The searches found 3884 studies, of which 31 were included in the review. A narrative synthesis was conducted for all the studies, and 18 studies were included in the meta-analyses. We found a positive association between heat exposure and mortality/morbidity related to the three diseases. With each 1 °C rise in temperature, cardiovascular and respiratory mortality risk increased by 2.1 % and 4.1 % respectively. The risk of cardiovascular morbidity was higher, at 6.7 %. A higher heat-related mortality and morbidity was also observed in those aged 65-years plus, and in women. These findings show populations in LMICs are vulnerable to adverse effects of heat exposure. The higher risk of morbidity outcomes is a novel finding and may indicate differential access to care and disease management.