Total sales in April dropped 1%, compared to the previous year, against market expectations of a 6.6% rise.
H&M managing director Rolf Eriksen said: "Considerably colder weather in most markets led to substantially weaker sales." However, he added: "The negative sales trend ended with warmer weather in the beginning of May. Sales during the first two weeks of May have been very satisfying."
The retailer currently trades from 1,560 stores.