Due to the increases in crude oil and typical seasonal advances, gasoline prices jumped nearly 20 cents per gallon in the past month, according to WEX’s February fuel prices report. But prices are still almost 30 cents per gallon lower than a year ago.

Prices usually run up in the spring when refiners shift from making winter gasoline to summer gasoline, a special spec mandated by the EPA, says WEX. Traders fear there won’t be enough supply on hand to meet the increased demand seen in the summer ― this panic drives prices higher. The peak typically comes in April or May, but last year the summit hit in late February, according to WEX.

Many analysts are surprised that the increases have not been as aggressive as anticipated. Most believe the bad weather has been a contributor. A recent survey showed gasoline demand was down more than 5% from 2013, which has helped keep prices at bay, says WEX.

But experts caution there could be a spring jolt as drivers, who have been stuck in their homes, start traveling again. As a result, many market-watchers still expect the national average to get close to $3.80 before Memorial Day.

Meanwhile, the national average for diesel has clawed its way above $4 per gallon again, says WEX. However, it is still more than 10 cents per gallon less than last year.