As Canadian grain companies spend millions to upgrade and build new export terminals in Vancouver, a new problem is threatening to cause transportation bottlenecks at the nation’s largest port: vessels can’t load grain in the rain. And it rains a lot in Vancouver.

In Canada’s wettest major city, the practice of loading ocean-bound vessels with grain in rainy weather has been halted since January amid safety concerns for marine crews.

“Vancouver terminals are generally operating on and off as the rain keeps starting and stopping,” said Wade Sobkowich, executive director of the Western Grain Elevator Association, which represents the nation’s grain shippers, including Richardson International, Cargill and Viterra, Glencore Plc’s Canadian grain unit. Earlier this week, “there were significant weather delays during the loading process” due to the rain.

The potential delays come as the port city heads into the wettest time of the year and as grain shippers seek to move large volumes of recently harvested crops including wheat and canola. November through January is the rainiest period of the year in Vancouver and there’s a chance this winter could be warmer and wetter than normal if El Nino conditions develop, said Matt MacDonald, a warning preparedness meteorologist with Environment Canada.