From Longman Dictionary of Contemporary Englishin bucketsin bucketsinformalLOT/LARGE NUMBER OR AMOUNT if rain comes down in buckets, it is raining very hard → bucket
Examples from the Corpus
in buckets• That night it came down in buckets.• The situation is modified when records are stored in buckets holding several records, but synonyms still occur.• Like rows of tulips in buckets waiting to be bought. 