The advice on climate-smart food consumption given by authorities and NGOs includes the recommendation to “eat seasonal foods”. However, no clear definition of seasonality is given in the literature. This study investigated how the carbon footprint of yearly per capita consumption of tomatoes and carrots in Sweden was affected by seasonal consumption according to interpretations of seasonality found in communications from Swedish NGOs and authorities. The results showed that the carbon footprint of carrot and tomato consumption was strongly affected by consuming according to either a strict definition of seasonality, which excluded both production in heated greenhouses and long-distance transport, or a definition which only allowed Swedish produce. The reduction potential was approximately 60%, but the consumption pattern was also highly restrictive, with e.g. tomatoes only being consumed during three months according to the strictest definition. The reduction from eating only Swedish products was not due primarily to characteristics commonly associated with seasonal production (shorter transport or low energy demand in cultivation), but to the use of renewable fuel instead of fossil energy. The methodology chosen in this study resulted in carrots having a more distinct season than tomatoes, since the energy use for heating greenhouses (which are needed all year round in cold climates) was evenly allocated across all tomatoes harvested during one year, while the carbon footprint of carrots was assumed to increase with time due to increased energy demand for storage and storage losses. Hence, modern production techniques challenge the traditional concepts of seasonality. On an absolute scale including the whole food sector, the reduction in greenhouse gas emissions from eating seasonal is limited, as emissions from vegetable production make up a minor proportion of the total emissions from food consumption.