You might have noticed gas prices inched up when you visited the fuel tanks this week.

You’re not imagining it: gas costs are up across Wisconsin, with prices rising more than 17 cents on average in the last week, according to AAA.

Here’s why gas prices are surging and which Wisconsin cities are feeling it the most.

Why are gas prices higher in Wisconsin this week?

A storm-related outage at an ExxonMobil facility in Illinois may be to blame for rising gas prices across the Upper Midwest this week, AAA said in a news release Thursday.

The refinery in Joliet, Illinois lost power earlier this month after a tornado touched down in the Chicago area on July 16. The facility, which processes 248,000 barrels per day, was about 50 miles from the tornado and battered by heavy wind and rain.

As of July 17, Reuters reported the refinery would be down for at least a week with plans to power back up in “late July.”

However, while the outage drives up prices across the Midwest, falling oil prices in the U.S. may help steady costs, AAA spokesperson Andrew Gross said in the news release.

“In April, a barrel of oil was in the upper $80s, but today, it is $10 a barrel cheaper. That might mitigate any upward pressure on pump prices,” Gross said.

Which Wisconsin cities have highest gas prices?

Counties in eastern Wisconsin are generally seeing the highest gas prices, while counties in the western half of the state are seeing prices 10 to 30 cents below Friday’s national average of $3.52 per gallon, according to AAA’s daily average gas prices tracker.

Most Wisconsin cities have seen gas prices tick up in the last week. Listed below are the average gas prices for a regular gallon of gas in major Wisconsin cities on Friday, compared to a week ago, according to AAA. All prices are rounded to the nearest hundredth of a cent.

Average gas prices in Wisconsin cities on July 26:

• Milwaukee-Waukesha: $3.80, up from $3.45 last week
• Madison: $3.45, up from $3. 43 last week
• Appleton: $3.44, up from $3.30 last week
• Eau Claire: $3.24, up from $3.20 last week
• Fond Du Lac: $3.37, same as $3.37 last week
• Green Bay: $3.50, up from $3.36 last week
• Kenosha County: $3.83, up from $3.50 last week
• Oshkosh: $3.44, up from $3.37 last week
• Racine: $3.78, up from $3.44 last week
• Sheboygan: $3.47, up from $3.33 last week
• Wausau: $3.47, up from $3.38 last week