The ZEMA graph above shows the North American natural gas spot prices on NYMEX for Henry Hub, Transco Zone 6, PG&E Citygate, and Chicago Citygates between November 01 – 30, 2015. Units are in USD/MMBtu.
On NYMEX, prices at Henry Hub and Chicago remained relatively similar at just below 2.40 USD/MMBtu throughout the first three weeks of November 2015. Henry Hub spot prices dropped to $2.14 USD/MMBtu on November 20, near the lowest levels since 2012. That is sharply down from the levels that Henry Hub traded over the summer, near $3 USD/MMBtu. The prices settled at 2.24 on November 30.
Prices at Transco 6, on the other hand fluctuated between 3.0 USD/MMBtu to 4.0 USD/MMBtu level at 3.93 USD/MMBtu on November 01 to 2.84 USD/MMBtu on November 16, and settled at 3.02 USD/ MMBtu on November 30. Prices at PG&E have been relatively stable, beginning the month at 2.76 USD/MMBtu, climbing to 2.86 USD/MMBtu on November 16, and falling down to 2.72 USD/MMBtu on November 30.
The fall in gas prices over the three weeks of November is a result of an oversupplied market and mild weather, supported by a new record of working gas in storage at 4,000 Bcf as of November 13.
Comparing November 2015 prices to the same period last year, monthly average gas prices decreased in Transco 6, Chicago Citygates, Henry Hub, and PG&E by 54%, 45%, 45%, and 41%, respectively as a result of oversupply of Natural Gas.
Source:  http://ir.eia.gov/ngs/ngs.html
Data Sources: NYMEX