Crude-oil futures finished lower, with ongoing concerns over a global glut of supplies keeping prices for the U.S. benchmark under $60 a barrel.

Meanwhile, natural-gas prices climbed nearly 5% Monday as warmer weather throughout much of the U.S. lifted prospects for cooling demand, and the potential for a storm in the Gulf of Mexico fed concerns over energy production and consumption in the region.

July natural gas jumped 13.9 cents, or 5.1%, to settle at $2.889 per million British thermal units on the New York Mercantile Exchange. Analysts attributed the spike in prices to warmer weather in much of the U.S., which raises cooling demand for natural gas and may limit increases for supplies in storage in the weeks to come.

On the oil front, July crude fell 44 cents, or 0.7%, to end at $59.52 a barrel, following a gain of 1.4% last week. July Brent crude which expired at the end of the session, fell $1.26, or 2%, to $62.61 a barrel on London’s ICE Futures exchange, while the more actively traded August crude finished at $63.95 a barrel, down 69 cents, or 1.1%. “Traders seem to be losing hope that the strategy of [Organization of the Petroleum Exporting Countries] is successfully stealing market share from competitors—even as U.S. oil rig counts continue to plummet,” said Matt Smith, director of commodity research at Clipper Data. Baker Hughes on Friday reported a 27th straight weekly decline in the number of U.S. rigs actively drilling for oil.

Data Friday from the U.S. Commodity Futures Trading Commission showed that speculative investors continued to pull out of the oil market. “Money managers were net sellers of 19,729 contracts of WTI crude oil in the week ended June 9, with long liquidation dominating the flow. The market is reducing what had been a moderately overbought condition,” Citi Futures said. Traders said speculative outflows could increase after the June 30 deadline for an Iranian nuclear deal if an agreement is reached with Tehran, paving the way for more Iranian crude to hit the market.