Analyzing seasonally resolved δ<sup>18</sup>O ice core data can aid the interpretation of the climate information in ice cores, providing also insights into factors governing the δ<sup>18</sup>O signal that cannot be deciphered by investigating the annual δ<sup>18</sup>O data only. However, the seasonal isotope signal has not yet to be investigated in northern Greenland, e.g. at the NEEM (North Greenland Eemian Ice Drilling) ice core drill site. Here we analyze seasonally resolved δ<sup>18</sup>O data from four shallow NEEM ice cores covering the last 150 years. Based on correlation analysis with observed temperature, we attribute about 70 % and 30 % of annual accumulation to summer and winter respectively. The NEEM summer δ<sup>18</sup>O signal correlates strongly with summer western Greenland coastal temperature and with the first principal component (PC1) of summer δ<sup>18</sup>O from multiple seasonally resolved ice cores from central/southern Greenland. However, there are no significant correlations between NEEM winter δ<sup>18</sup>O data and western Greenland coastal winter temperature, or southern/central Greenland winter δ<sup>18</sup>O PC1. The stronger correlation with temperature during summer and the dominance of summer precipitation skew the annual δ<sup>18</sup>O signal in NEEM. The strong footprint of temperature in NEEM summer δ<sup>18</sup>O record also suggests that the summer δ<sup>18</sup>O record, rather than the winter δ<sup>18</sup>O record, is a better temperature proxy at the NEEM site. Despite dominant signal of North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) in the central-southern ice cores data, both NAO and AMO exert weak influences on NEEM seasonal δ<sup>18</sup>O variations. The NEEM seasonal δ<sup>18</sup>O is found to be highly correlated with Baffin Bay sea ice concentration (SIC) in satellite observation period (1979–2004), suggesting a connection of the sea ice extent with δ<sup>18</sup>O at NEEM. NEEM winter δ<sup>18</sup>O significantly correlates with SIC even for the period prior to satellite observation (1901–1978). The NEEM winter δ<sup>18</sup>O may reflect sea ice variations of Baffin Bay rather than temperature itself. This study shows that seasonally resolved δ<sup>18</sup>O records, especially for sites with seasonal precipitation bias such as NEEM, provide a better understanding of how changing air temperature and circulation patterns are associated with the variability of the δ<sup>18</sup>O records.