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15. Montpelier, Vermont
> Avg. temperature, Sept. 2021: 61.1 °F
> Change from avg. Sept. temperature, 1901-2000: +5.8
> Hottest September on record: 1961 (Avg temperature: 63.1 °F)
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14. Billings, Montana
> Avg. temperature, Sept. 2021: 65.2 °F
> Change from avg. Sept. temperature, 1901-2000: +5.8
> Hottest September on record: 2009 (Avg temperature: 66.7 °F)
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13. Sheridan, Wyoming
> Avg. temperature, Sept. 2021: 62.9 °F
> Change from avg. Sept. temperature, 1901-2000: +5.9
> Hottest September on record: 1963 (Avg temperature: 64.3 °F)
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12. Wausau, Wisconsin
> Avg. temperature, Sept. 2021: 63.3 °F
> Change from avg. Sept. temperature, 1901-2000: +6.0
> Hottest September on record: 2015 (Avg temperature: 64.9 °F)
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11. Bismarck, North Dakota
> Avg. temperature, Sept. 2021: 65.1 °F
> Change from avg. Sept. temperature, 1901-2000: +6.2
> Hottest September on record: 1948 (Avg temperature: 66.1 °F)