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+---
+title: "SPEC 4 — Nightly Wheels"
+date: 2022-09-05
+author:
+  - "Jarrod Millman <millman@berkeley.edu>"
+  - "Matthew Feickert <matthew.feickert@cern.ch>"
+  - "Olivier Grisel <olivier.grisel@ensta.org>"
+discussion: https://discuss.scientific-python.org/t/spec-4-nightly-wheels/474
+endorsed-by:
+---
+
+## Description
+
+<!--
+Briefly and clearly describe the proposal.
+Explain the general need and the advantages of this specific proposal.
+If relevant, include examples of how the new functionality would be used,
+intended use-cases, and pseudo-code illustrating its use.
+-->
+
+This SPEC recommends that projects test against nightly wheels of several
+widely-used projects in the Scientific Python ecosystem.
+
+There are two main motivations for this recommendation:
+
+1. Testing against nightly wheels will help identify when changes to the main branch
+   of the widely-used projects break downstream projects.
+2. By using the nightly wheels projects will not have to build packages from source,
+   which can be difficult and time consumming.
+
+## Implementation
+
+<!--
+Discuss how this would be implemented.
+-->
+
+We recommend that projects add a cron job to test against the nightly wheels and
+when errors are encountered to automatically open an issue in their project so they
+can investigate.
+
+The nightly wheels for conda can be found [here](https://anaconda.org/scientific-python-nightly-wheels/).
+
+We have a GitHub action to upload new nightly wheels and remove old ones:
+https://github.com/scientific-python/nightly-wheels
+
+### Core Project Endorsement
+
+<!--
+Discuss what it means for a core project to endorse this SPEC.
+-->
+
+### Ecosystem Adoption
+
+<!--
+Discuss what it means for a project to adopt this SPEC.
+-->
+
+## Notes
+
+<!--
+Include a bulleted list of annotated links, comments,
+and other ancillary information as needed.
+-->