OTTR

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually pursuant to Restricted Stock Award distributions and shares received pursuant to Otter Tail Corporation's Compensation Plan for Outside Directors.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

Each restricted stock unit represents a contingent right to receive a cash payment equal to the fair market value of one share of Otter Tail Corporation common stock upon vesting.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually through the Dividend Reinvestment Plan and shares acquired individually pursuant to Restricted Stock Award distributions.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest on April 8, 2031.

Shares of Common Stock acquired under the 2023 Stock Incentive Plan, which is a grant of Restricted Stock. The shares granted on April 13, 2026 will vest in near-equal installments of one-third per year beginning April 8, 2027.

This grant has a fair market value of $91.15.

Total direct holdings include shares acquired individually and pursuant to Restricted Stock Award distributions.

The reporting person receives one share of Common Stock for each restricted stock unit that vests.

Total direct holdings include shares acquired through the dividend reinvestment plan, the Employee Stock Purchase Plan, and shares acquired pursuant to restricted stock unit distributions.

Total direct holdings include shares acquired through the dividend reinvestment plan, the Employee Stock Purchase Plan, and shares acquired pursuant to restricted stock unit distributions.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired individually through dividend reinvestment, Employee Stock Purchase Plan, and acquired pursuant to Restricted Stock Awards and Performance Share Awards

Represents shares received upon the vesting of certain performance criteria in connection with a Performance Share Award (granted in 2023).

Represents shares received upon the vesting of certain performance criteria in connection with a Performance Share Award (granted in 2023).

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired individually pursuant to Restricted Stock Awards and Performance Shares Awards.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired through the Dividend Reinvestment Plan, the Employee Stock Purchase Plan and shares acquired pursuant to Stock Options, Restricted Stock Awards, Restricted Stock Units and Performance Share Awards.

Represents shares received upon the vesting of certain performance criteria in connection with a Performance Share Award (granted in 2023).

Represents shares received upon the vesting of certain performance criteria in connection with a Performance Share Award (granted in 2023).

Represents shares received upon the vesting of certain performance criteria in connection with a Performance Share Award (granted in 2023).

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares held jointly with spouse and shares acquired through the Employee Stock Purchase Plan, the Dividend Reinvestment Plan, and shares acquired pursuant to Restricted Stock Awards and Performance Share Awards.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired individually through dividend reinvestment, Employee Stock Purchase Plan, and acquired pursuant to Restricted Stock Awards and Performance Share Awards.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired individually pursuant to Restricted Stock Awards and Performance Shares Awards.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired individually through dividend reinvestment, Employee Stock Purchase Plan, and acquired pursuant to Restricted Stock Awards and Performance Share Awards.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

Each restricted stock unit represents a contingent right to receive one share of Otter Tail Corporation stock.

The restricted stock units vest in four equal annual installments beginning the date shown above.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares acquired through the dividend reinvestment plan, the Employee Stock Purchase Plan, and shares acquired pursuant to restricted stock unit distributions.

These shares were withheld by the Corporation to pay taxes due upon vesting of this award, exempt pursuant to Rule 16b-3(e).

Total direct holdings include shares held jointly with spouse and shares acquired through the Employee Stock Purchase Plan, the Dividend Reinvestment Plan, and shares acquired pursuant to Restricted Stock Awards and Performance Share Awards.