LONDON, Jan 23 (Reuters) - U.S. natural gas prices have bounced sharply from their lows in December after a sustained spell of exceptionally cold temperatures pushed stocks near to the bottom of their five-year range.

Futures prices for gas delivered to Henry Hub in February have risen more than 25 percent since Dec. 21. Prices for deliveries in July are up 10 percent.

The tightening calendar spread, with prompt prices rising much faster than those for deferred contracts, is consistent with a market that is undersupplied and trying to conserve remaining stocks.

Rising near-term prices should discourage gas consumption by electric generators in favour of coal while sending a signal to gas producers to increase drilling and output (http://tmsnrt.rs/2E1ZV8Q).

Gas stocks have been tightening progressively for 10 months, turning a surplus of 400 billion cubic feet (bcf) to the five-year average in March 2017 into a deficit of 200 bcf by the end of the year.

Tightening stocks were not enough to support prices, which fell steadily between May and the week before Christmas.