Winters in Grantham are typically cold and variable, with January temperatures averaging around 3°C, fluctuating between -7°C and 12°C. February brings a slight warming trend, with averages rising to 5°C. As spring approaches, March sees significant temperature increases, with averages reaching 7°C, while April's averages remain steady at 6°C. Summers are mild, with June and July temperatures averaging around 16-18°C, although occasional heatwaves can push temperatures up to 26-29°C. Autumn brings a cooling trend, with October temperatures averaging 12°C, before dropping back down in November and December, which see averages of 8°C and 6°C respectively.