diff --git a/README.md b/README.md
index 0a02163..6bdb99e 100644
--- a/README.md
+++ b/README.md
@@ -24,8 +24,15 @@ pre-commit install
 For making changes, see the [guidance on development](https://github.com/alan-turing-institute/python-project-template?tab=readme-ov-file#setting-up-a-new-project) from the template that generated this project.
 
 ## Usage
+
+Example:
+
+```bash
+cloudcasting download "2020-06-01 00:00" "2020-06-30 23:55" "path/to/my/dir/data.zarr"
+```
+
 ```bash
- cloudcasting download --help
+> cloudcasting download --help
 
  Usage: cloudcasting download [OPTIONS] START_DATE END_DATE OUTPUT_DIRECTORY
 
@@ -57,37 +64,38 @@ For making changes, see the [guidance on development](https://github.com/alan-tu
 │                                  [default: None]                               │
 │                                  [required]                                    │
 ╰────────────────────────────────────────────────────────────────────────────────╯
-╭─ Options ──────────────────────────────────────────────────────────────────────╮
-│ --data-inner-steps                              INTEGER  Data will be sliced   │
-│                                                          into                  │
-│                                                          data_inner_steps*5mi… │
-│                                                          chunks                │
-│                                                          [default: 3]          │
-│ --get-hrv                --no-get-hrv                    Whether to download   │
-│                                                          HRV data              │
-│                                                          [default: no-get-hrv] │
-│ --override-date-boun…    --no-override-date…             Whether to override   │
-│                                                          date range limits     │
-│                                                          [default:             │
-│                                                          no-override-date-bou… │
-│ --lon-min                                       FLOAT    Minimum longitude     │
-│                                                          [default: -16]        │
-│ --lon-max                                       FLOAT    Maximum longitude     │
-│                                                          [default: 10]         │
-│ --lat-min                                       FLOAT    Minimum latitude      │
-│                                                          [default: 45]         │
-│ --lat-max                                       FLOAT    Maximum latitude      │
-│                                                          [default: 70]         │
-│ --help                                                   Show this message and │
-│                                                          exit.                 │
-╰────────────────────────────────────────────────────────────────────────────────╯
-
-```
+╭─ Options ─────────────────────────────────────────────────────────────────────╮
+│ --data-inner-steps                             INTEGER  Data will be sliced   │
+│                                                         into                  │
+│                                                         data_inner_steps*5mi… │
+│                                                         chunks                │
+│                                                         [default: 3]          │
+│ --get-hrv               --no-get-hrv                    Whether to download   │
+│                                                         HRV data              │
+│                                                         [default: no-get-hrv] │
+│ --override-date-bou…    --no-override-date…             Whether to override   │
+│                                                         date range limits     │
+│                                                         [default:             │
+│                                                         no-override-date-bou… │
+│ --lon-min                                      FLOAT    Minimum longitude     │
+│                                                         [default: -16]        │
+│ --lon-max                                      FLOAT    Maximum longitude     │
+│                                                         [default: 10]         │
+│ --lat-min                                      FLOAT    Minimum latitude      │
+│                                                         [default: 45]         │
+│ --lat-max                                      FLOAT    Maximum latitude      │
+│                                                         [default: 70]         │
+│ --valid-set             --no-valid-set                  Whether to filter     │
+│                                                         data from 2022 to     │
+│                                                         download the          │
+│                                                         validation set (every │
+│                                                         2 weeks).             │
+│                                                         [default:             │
+│                                                         no-valid-set]         │
+│ --help                                                  Show this message and │
+│                                                         exit.                 │
+╰───────────────────────────────────────────────────────────────────────────────╯
 
-Example:
-
-```bash
-cloudcasting download "2020-06-01 00:00" "2020-06-30 23:55" "path/to/my/dir/data.zarr"
 ```
 
 
diff --git a/src/cloudcasting/download.py b/src/cloudcasting/download.py
index d7e5f3c..47eb132 100644
--- a/src/cloudcasting/download.py
+++ b/src/cloudcasting/download.py
@@ -84,6 +84,12 @@ def download_satellite_data(
     lon_max: Annotated[float, typer.Option(help="Maximum longitude")] = 10,
     lat_min: Annotated[float, typer.Option(help="Minimum latitude")] = 45,
     lat_max: Annotated[float, typer.Option(help="Maximum latitude")] = 70,
+    valid_set: Annotated[
+        bool,
+        typer.Option(
+            help="Whether to filter data from 2022 to download the validation set (every 2 weeks)."
+        ),
+    ] = False,
 ) -> None:
     """
     Download a selection of the available EUMETSAT data.
@@ -154,6 +160,21 @@ def download_satellite_data(
         # in `data_inner_steps` (which should be slighly more robust to missing values).
         ds = ds.sel(time=np.mod(ds.time.dt.minute, data_inner_steps * 5) == 0)
 
+        if year == 2022:
+            set_str = "Validation" if valid_set else "Training"
+            week_str = "3" if valid_set else "1"
+            logger.info("Data in 2022 will be downloaded every 2 weeks due to train/valid split.")
+            logger.info("%s set selected: starting week will be %s", set_str, week_str)
+            # integer division by 14 will tell us the week we're on.
+            # checking the mod wrt 2 will let us select ever 2 weeks (weeks are 1-indexed).
+            # valid set is defined as from week 3-4, 7-8 etc. (where the mod is != 2).
+            mask = (
+                np.mod(ds.time.dt.day // 14, 2) != 0
+                if valid_set
+                else np.mod(ds.time.dt.day // 14, 2) == 0
+            )
+            ds = ds.sel(time=mask)
+
         # Convert lon-lat bounds to geostationary-coords
         (x_min, x_max), (y_min, y_max) = lon_lat_to_geostationary_area_coords(
             [lon_min, lon_max],