We studied the effect of cooling rate on responses of cucumber plants (Cucumis sativus L.) to a daily short-term (2 hour) temperature reduction (DROP) at the end of the night (dark DROP) or at the beginning of the day (light DROP). The temperature was lowered from 20° to 9 °C gradually (at a rate of 0.4 °C/min) or sharply (11 °C/min) by transferring plants from one climate chamber to another. This work has shown that under short-term exposure to low non-injurious temperatures a fast versus slow cooling have somewhat different effects on plants. DROP with rapid cooling had a more pronounced negative impact on the state of the photosynthetic apparatus of the plants and biomass accumulation compared to DROP with slow temperature decrease. The differences were more pronounced when plants were treated by light DROP, which indicates that the time of day, or rather the presence or absence of light at a time when the plants are exposed to low temperature plays a significant role. At the same time, a plant height, leaf emergence rate and leaf chilling tolerance changed under the influence of DROP regardless of the cooling rate. All these factors should be considered in laboratory experiments, when low temperature effects on plants are studied at rapid cooling, when temperature changes are achieved by transferring plants from one growth chamber to another.