NORTHWEST NATURAL GAS CO

Q: Jun 30 2026

Q: Mar 31 2026

FY: Dec 31 2025

Q: Sep 30 2025

Q: Jun 30 2025

Q: Mar 31 2025

FY: Dec 31 2024

Q: Sep 30 2024

Q: Jun 30 2024

Q: Mar 31 2024

FY: Dec 31 2023

Q: Sep 30 2023

Q: Jun 30 2023

Q: Mar 31 2023

FY: Dec 31 2022

Q: Sep 30 2022

Q: Jun 30 2022

Q: Mar 31 2022

FY: Dec 31 2021

Q: Sep 30 2021

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

Results of Operations and Financial Condition

Other Events

Results of Operations and Financial Condition

Other Events

Results of Operations and Financial Condition

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Results of Operations and Financial Condition

Other Events

Other Events

Results of Operations and Financial Condition

Other Events

Results of Operations and Financial Condition

Results of Operations and Financial Condition

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Other Events

2.02,9.01

Regulation FD Disclosure

5.02,7.01,9.01

Automatic Shelf Registration

Prospectus Supplement for Delayed or Continuous Offering

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Prospectus Supplement for Delayed or Continuous Offering

Prospectus Supplement for Primary Offering

Free Writing Prospectus

Prospectus Supplement for Primary Offering

Free Writing Prospectus

Prospectus Supplement for Primary Offering

Prospectus Supplement for Delayed or Continuous Offering

Automatic Shelf Registration

Prospectus Supplement for Primary Offering

Free Writing Prospectus

Prospectus Supplement for Primary Offering

Free Writing Prospectus

Certification of termination of registration of a class of securities (Section 12(b))

Notification of removal from listing and/or registration on a national securities exchange

Post Effective Amendment to S-8

Post Effective Amendment to S-8

Post Effective Amendment to S-8

Definitive Proxy Statement

Definitive Proxy Statement

Required Information in Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Preliminary Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Preliminary Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

Definitive Proxy Statement

HUDDLESTON JON G

Weber David A.

Saathoff MardiLyn

DOOLITTLE LEA ANNE

ANDERSON DAVID HUGO

GIBSON C SCOTT

Wilhoite Charles A.

Rogers Melinda B.

Wasson Malia H

BOYLE TIMOTHY P

Byorum Martha L

CARTER JOHN D

DODSON MARK S

GIBSON C SCOTT

HAMACHEK TOD R

Peverett Jane L

Thrasher Kenneth

ANDERSON DAVID HUGO

HUDDLESTON JON G

Imeson Thomas J

Annual Report Scanned (Paper)

Annual Report Scanned (Paper)

Annual Report Scanned (Paper)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual Report Scanned (Paper)

Letter from the SEC

Letter from the SEC

Post-effective amendment to an automatic shelf registration statement

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Letter from the SEC

Correspondence with the SEC

Correspondence with the SEC

Letter from the SEC

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Correspondence with the SEC

Correspondence with the SEC

Letter from the SEC

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual Report Scanned (Paper)