ABILENE, Texas -

Gas prices around Abilene Thursday were about $3.69 per gallon.

Retail gasoline prices across the state have jumped 21 cents in the past week as U.S. refineries prepare to switch to a more expensive summer-blend gas.

The state average for gas is $3.64 per gallon for regular.

The nationwide average price of gasoline rose 15 cents this week.  It's now at $3.78 per gallon.

AAA said the updated gasoline blend is expected to reach markets in a couple of weeks but until then prices at the pump could continue to rise.