However, the R NDVI-TMX and R NDVI-TMN changed little in mid-latitudes. The positive correlation between NDVI and TMX (R NDVI-TMX) weakened in high latitudes, as well as the negative correlation between NDVI and TMN (R NDVI-TMN). Under the asymmetric diurnal warming, the effects of TMX and TMN on normalized difference vegetation index (NDVI) exhibited distinct temporal variations between mid- (55 °N). The results showed there had been significant warming trends in growing season maximum (TMX, 0.37 ☌ per decade) and minimum temperatures (TMN, 0.38 ☌ per decade) during 1982–2015, especially in high latitudes of the NH. To improve our understanding on the relationship between vegetation growth and global warming, this study tries to attribute the respective effects of daytime and nighttime temperature on vegetation growth and reveal their temporal trends in the extratropical Northern Hemisphere (30–90 °N). Among the set of possible driving forces, the asymmetric daytime and nighttime warming effect has been largely neglected. Global warming has boosted vegetation growth to a large extent, but this stimulation effect has significantly weakened in recent years.