Cities Skylines II Seasonal Shift 1.6.4f1: Patch Notes, Mods and Hydropower Fixes

Cities Skylines II Seasonal Shift 1.6.4f1 arrived on 10 November 2026, fixing the Hydroelectric Power Plant, a simulation bug that could slow down cities, and several Paradox Mods issues. The free PC patch also changes the interface and graphics support.

The Cities Skylines II Seasonal Shift 1.6.4f1 patch also makes a new Grand Post Office signature building available through a Paradox newsletter subscription. It prepares the game for Park Adventures, but the paid DLC, with its park districts and attractions, is scheduled for 2 December. Here is what you can actually use following the November update, and what still has to wait.

What is included in Cities Skylines II Seasonal Shift 1.6.4f1?

The headline fix in Cities Skylines II Seasonal Shift 1.6.4f1 concerns cities accumulating companies that have no buildings to occupy. Iceflake says this could cause performance problems as the simulation grew. The patch addresses that particular issue; it should not be mistaken for a guarantee that every large city now runs smoothly on every PC.

If your Hydroelectric Power Plant stopped working, this is one of the more useful fixes. The patch fixes a malfunction, but a dam still needs suitable terrain and water flow to generate electricity.

Paradox Mods changes in Cities Skylines II Seasonal Shift 1.6.4f1

Cities Skylines II Seasonal Shift 1.6.4f1 introduces a By followed creators tab and a featured area showing newer content from creators you follow. Follow badges appear on creator avatars, and subscribed playsets now have a Follow latest playset version setting. You can also change a mod’s visibility through the Paradox Mods interface.

Cities Skylines II Seasonal Shift 1.6.4f1 also fixes several frustrating edge cases: mod content sometimes failing to load when selecting Continue from the launcher, playsets or the Mods interface failing to appear on startup, and subscribed mods disappearing from a playset after downloads failed. Players who subscribed to multiple mods should also benefit from fixes for untracked downloads.

Shared playsets received attention as well. The changelog addresses wrong-version openings, endless loading when visiting a creator’s shared playset, and problems managing a Library while offline. Logged-out players can now open and manage Playsets and Library, while creators can show shared playsets without being signed in. Our mod-loading troubleshooting guide separates these fixes from problems that can still come from an individual mod.

Graphics updates and features that have not arrived

The graphics section of Cities Skylines II Seasonal Shift 1.6.4f1 lists NVIDIA DLSS 4.5, AMD FSR 3 and Intel XeSS 3. It also notes a refreshed benchmark save. The notes do not promise specific FPS gains; actual results will depend on your hardware and city.

Two changes mentioned in the developer’s follow-up are not part of this release. Iceflake held back FSR4 support and extra texturing beneath roads for further work following player feedback. If you’re looking for either option, do not treat the November patch as confirmation it has shipped.

Grand Post Office unlock and December DLC

There is one bonus building connected to Cities Skylines II Seasonal Shift 1.6.4f1: the Grand Post Office. Paradox says it is a signature building unlocked by subscribing to the publisher’s newsletter. It is a separate reward from the Downtown Market Set and from the upcoming park expansion. The precise in-game menu position, building cost and account-linking process are not set out in the patch notes, so we have avoided inventing a click-by-click sequence. See our Grand Post Office unlock guide for the confirmed requirement.

Park Adventures itself is still due on 2 December 2026 for PC, with four park categories, district-based building and five new maps. The free environment work and additional Editor biomes planned alongside it are also separate from what Seasonal Shift delivered on 10 November. You can check our Park Adventures release guide and new biomes explainer before buying anything.

Paradox additionally announced a Steam free-to-play period for 12 to 16 November. That is a temporary trial window, not a permanent copy of the game, and the sale or access state can change independently of Cities Skylines II Seasonal Shift 1.6.4f1. Anyone deciding whether to buy should check the Steam listing rather than assuming access remains active after the announced period.

Is Seasonal Shift worth installing now?

If your mods vanished when you used Continue, playsets refused to load or your hydroelectric plant stopped working, the update addresses those reported bugs. If you play without mods, the company-simulation and interface changes are still relevant. Owners do not need Park Adventures to receive the base-game patch.

Seasonal Shift is live now, while the park districts, rides and new maps are coming with the December expansion. The changelog below has the full list of November fixes.

Official source: Paradox Interactive / Iceflake Studios: Patch 1.6.4f1 Seasonal Shift.