Two European energy companies said Thursday their fiscal performance was hurt by a mild winter, while the demand economy showed signs of slowing down.

German energy company RWE said "persistently low prices" and "unusually mild weather" was in part to blame for the 31 percent decline in operating results year-on-year to $3.6 billion.

French company GDF Suez in its quarterly report said revenues were down for the first nine months of the year because of "the unfavorable impact of weather on natural gas sales."

GDF Suez said 2013 was a particularly cold year for the European community, while this year has been generally mild.

Forecasting website Accuweather said some parts of Europe are in store for the harshest winter in several years for the upcoming season.

While that should lead to an increase in winter heating demands, a report Thursday from the European Central Bank said falling crude oil prices and geopolitical tensions in Eastern Europe could dampen economic growth forecasts.

"The balance of risks has become more clearly tilted to the downside," the report read.

For RWE, at least, it said it was keeping its outlook for 2015 unchanged.