diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 08b45268..21f7b6ad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,6 +3,8 @@ on: [push, pull_request, workflow_dispatch]
 jobs:
   run:
     runs-on: ubuntu-latest
+    env:
+      REGISTRY_PORT: 5000
     steps:
 
     - uses: actions/checkout@v2
@@ -20,7 +22,9 @@ jobs:
       # and hyphens.
       run: echo "TAG=branch-${GITHUB_REF_NAME//[^A-Za-z0-9._-]/-}" | tee -a $GITHUB_ENV
 
-    - run: ./devel/build $TAG
+    - run: ./devel/start-localhost-registry $REGISTRY_PORT
+
+    - run: ./devel/build -r localhost:$REGISTRY_PORT -t $TAG
 
     - if: github.event_name != 'pull_request'
       uses: docker/login-action@v1
@@ -46,3 +50,6 @@ jobs:
       run: |
         ./devel/tag-latest $TAG
         ./devel/push latest $TAG
+
+    - if: always()
+      run: ./devel/stop-localhost-registry
diff --git a/README.md b/README.md
index ed32ff9e..437b6cf3 100644
--- a/README.md
+++ b/README.md
@@ -28,14 +28,27 @@ This is most helpful when you want the image to contain the latest version of a
 
 ### Building
 
-To build this image locally, run:
+To build this image locally,
 
-```
-./devel/build
-```
+1. Start a local Docker registry.
 
-By default, this tags the image with `latest`. If you want to use a custom tag
-name, you can specify it as the first argument to the script.
+    ```
+    ./devel/start-localhost-registry
+    ```
+
+    It will be served at `localhost:5000`. Optionally, specify another port as
+    an argument. Running a local Docker registry allows us to mimic direct push
+    to a registry done in the GitHub Actions CI workflow.
+
+2. Build the image.
+
+    ```
+    ./devel/build
+    ```
+
+    By default, this tags the image with `latest` and pushes to
+    `localhost:5000`. See instructions at the top of the script for additional
+    options.
 
 On each subsequent change during your development iterations, you can run just
 the `./devel/build` command again.
diff --git a/devel/build b/devel/build
index a485760a..b0e498eb 100755
--- a/devel/build
+++ b/devel/build
@@ -1,10 +1,11 @@
 #!/bin/bash
 #
 # Builds the nextstrain/base and nextstrain/base-builder images with useful
-# caching.
+# caching and pushes to a registry.
 #
-# By default this tags images using "latest", but you can provide a custom tag
-# name.
+# By default this tags images using "latest" and pushes to localhost:5000, but
+# you can provide a custom tag with -t <tag> and specify a different
+# registry with -r <registry>.
 #
 # Set CACHE_DATE in your environment to force layers after our custom cache
 # point to be re-built. See the ARG CACHE_DATE line in the Dockerfile for more
@@ -12,8 +13,18 @@
 #
 set -euo pipefail
 
-# If the tag is not provided, default to "latest".
-tag="${1:-latest}"
+# Set default values.
+registry=localhost:5000
+tag=latest
+
+# Read command-line arguments.
+while getopts "r:t:" opt; do
+    case "$opt" in
+        r) registry="$OPTARG";;
+        t) tag="$OPTARG";;
+        *) echo "Usage: $0 [-r <registry>] [-t <tag>]" 1>&2; exit 1;;
+    esac
+done
 
 export GIT_REVISION=$(git describe --tags --abbrev=40 --always --dirty || true)
 
@@ -36,7 +47,7 @@ if ! docker buildx inspect "$builder" &>/dev/null; then
     # However, if this is changed and it was previously run on your machine,
     # you may need to remove the builder manually before running the script:
     #     docker builder rm "nextstrain-builder"
-    docker buildx create --name "$builder" --driver docker-container
+    docker buildx create --name "$builder" --driver docker-container --driver-opt network=host
 fi
 
 BUILDER_IMAGE=nextstrain/base-builder
@@ -51,8 +62,8 @@ docker buildx build \
     --cache-from "$BUILDER_IMAGE:latest" \
     --cache-from "$BUILDER_IMAGE:$tag" \
     --cache-to type=inline \
-    --tag "$BUILDER_IMAGE:$tag" \
-    --load \
+    --tag "$registry/$BUILDER_IMAGE:$tag" \
+    --push \
     .
 
 docker buildx build \
@@ -66,6 +77,6 @@ docker buildx build \
     --cache-from "$FINAL_IMAGE:latest" \
     --cache-from "$FINAL_IMAGE:$tag" \
     --cache-to type=inline \
-    --tag "$FINAL_IMAGE:$tag" \
-    --load \
+    --tag "$registry/$FINAL_IMAGE:$tag" \
+    --push \
     .
diff --git a/devel/start-localhost-registry b/devel/start-localhost-registry
new file mode 100755
index 00000000..9a92e17b
--- /dev/null
+++ b/devel/start-localhost-registry
@@ -0,0 +1,16 @@
+#!/bin/bash
+#
+# Starts a Docker registry on localhost using a Docker container.
+#
+set -euo pipefail
+
+# Port to run the registry on. If not provided, default to 5000.
+PORT="${1:-5000}"
+
+# Name of the docker container.
+NAME=nextstrain-local-registry
+
+# Docker image that provides the registry service.
+IMAGE=registry:2
+
+docker run -d -p "$PORT":"$PORT" --restart always --name "$NAME" "$IMAGE" > /dev/null
diff --git a/devel/stop-localhost-registry b/devel/stop-localhost-registry
new file mode 100755
index 00000000..30919fb1
--- /dev/null
+++ b/devel/stop-localhost-registry
@@ -0,0 +1,10 @@
+#!/bin/bash
+#
+# Stops a local Docker registry created by start-localhost-registry.
+#
+set -euo pipefail
+
+NAME=nextstrain-local-registry
+
+docker stop "$NAME" > /dev/null
+docker rm "$NAME" > /dev/null