Gas prices have been spiking for weeks and $4 gas is quickly becoming a reality across the nation.

Illinois became the latest state to succumb, with motorist group AAA reporting Tuesday that the average price for a gallon of gas in the state had hit $4.03 a gallon. On Wednesday, the average price in Illinois nudged up to $4.04 a gallon.

There are now four U.S. states with gas prices above what many economists consider a 'tipping point' for consumers. Prices in California, Alaska and Hawaii have been above $4 a gallon for weeks.

As of Wednesday, the national average stood at $3.81 a gallon. While that's still below the $4 mark, prices are up 24% from the start of the year.

A big culprit behind the surge has been oil. While gas prices typically start to rise at this time of year, $100 oil isn't helping.

Based on current oil prices, there is a 33% chance that the national average gas price could hit $4 a gallon in July, said the Energy Information Administration in its April short-term energy outlook.

But the EIA isn't ringing the $4 panic bell just yet, calling for gas prices to average $3.86 a gallon this summer. That would still translate into a whopping 40% rise from last summer.

via Drivers: Brace for $4 a gallon gas this summer - Apr. 12, 2011.