Investor Presentaiton

L Heating Degree - Days Montana South Dakota Nebraska Appendix 42 Weather (Fourth Quarter) Qtr 4 Degree Days Q4 2020 as compared with: Historic Historic 2020 2019 Average 2,798 3,043 2,956 2019 8% warmer Average 5% warmer 1,881 2,128 2,016 12% warmer 7% warmer 1,426 1,705 1,681 16% warmer 15% warmer We estimate unfavorable weather for the 4th quarter 2020 has contributed approximately $5.7M pretax detriment as compared to normal and $5.0M pretax detriment as compared to the same period in 2019. Difference from Average Temperatures October 2020 November 2020 December 2020 -15 -12 -3 0 3 12 15 Degrees Fahrenheit from Average NorthWestern Energy Delivering a Bright Future

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