The hypothetical NGL barrel at Mont Belvieu, Texas, rose above $37 a barrel last week for the first time since the first week of October 2014. Not coincidentally, that was also the last time that propane eclipsed $1 a gallon (gal).

To calculate propane’s current trend requires a check on the weather. Not this year’s weather—last year’s.

It’s been a year since Hurricane Harvey walloped the Gulf Coast with massive rainfall and brought the refining and export complex to its knees. The U.S. Energy Information Administration (EIA) estimated days of supply for propane at 65.8 on Aug. 25, 2017, the day Harvey made landfall on the Texas coast at San Jose Island. The EIA’s next weekly estimate, on Sept. 1, raised the days of supply to 86.8.