The Energy Information Administration (EIA) Natural Gas Storage report measures the change in the number of cubic feet of natural gas held in underground storage during the past week.

While this is a U.S. indicator it tends to have a greater impact on the Canadian dollar, due to Canada's sizable energy sector.

If the increase in natural gas inventories is more than expected, it implies weaker demand and is bearish for natural gas prices. The same can be said if a decline in inventories is less than expected.
If the increase in natural gas is less than expected, it implies greater demand and is bullish for natural gas prices. The same can be said if a decline in inventories is more than expected.