A dose rate is quantity of radiation absorbed or delivered per unit time.
When considering stochastic radiation effects, only the total dose is relevant; each incremental unit of dose increases the probability that the stochastic effect happens.
The total dose can be above the threshold for a deterministic effect, but if the dose is spread out over a long period of time, the effect is not observed.
Consider the sunburn, a deterministic effect:[4] when exposed to bright sunlight for only ten minutes[5] at a high UV Index, that is to say a high average dose rate,[6] the skin can turn red and painful.
The same total amount of energy from indirect sunlight spread out over several years - a low average dose rate - would not cause a sunburn at all, although it may still cause skin cancer.