To create a minimalist background for an Astro forecast component, you can use the astro package's built-in styling options. Here is a brief example of how to achieve this using CSS:

/* Add this to your astro.config.js file */
import { css } from '@astrojs/css';

export default {
  // ... other configurations ...
  styles: [
    css`
      body {
        background-color: #f0f0f0; /* Light gray background */
        font-family: Arial, sans-serif;
      }
    `,
  ],
};

This will set a light gray background for the entire page. You can adjust the color and other styling options to fit your desired minimalist design.

For a more specific solution, you may want to consider using a library like @astrojs/typography or @astrojs/styles to create a custom typography system for your Astro application.