Hello,
it seems using ansi-color-apply in Emacs-28 is not working properly,
there is no colors.  In Emacs-29 it is working properly (very nice)
without needing a workaround used previously in emacs-27 (code commented).
See code below to reproduce and Screenshots attached.

Thanks.

#+begin_src elisp

(defvar wttr-weather-history nil)
(defvar wttr-weather-default-location "Guillestre")
(defvar wttr-weather-last-location nil)
;;;###autoload
(defun wttr-weather (place)
  "Weather forecast with wttr.in.
With a prefix arg refresh buffer if some.
See <https://github.com/chubin/wttr.in>."
  (interactive (list (read-string (format "Place (%s): "
                                          wttr-weather-default-location)
                                  nil
                                  'wttr-weather-history
                                  wttr-weather-default-location)))
  (let ((buf (get-buffer-create (format "*wttr.in %s*" place))))
    (switch-to-buffer buf)
    (when current-prefix-arg
      (set (make-local-variable 'wttr-weather-last-location) nil))
    (unless wttr-weather-last-location
      (wttr-weather-update place)
      (wttr-weather-mode)
      (set (make-local-variable 'wttr-weather-last-location) place))))

(defun wttr-weather-update (place)
  (let* ((inhibit-read-only t)
         ansi
         (data
          (with-temp-buffer
            (call-process
             "curl" nil '(t t) nil
             "-s" (format "fr.wttr.in/~%s?m" (shell-quote-argument place)))
            (goto-char (point-min))
            ;; Commenting this part which is for Emacs-27.
            ;; `ansi' is not set but it is not a problem for just
            ;; debugging this.
            ;;
            ;; (while (re-search-forward "38;5;\\([0-9]+\\)m" nil t)
            ;;   ;; If we have ansi sequences, that's mean we had weather
            ;;   ;; output, otherwise we have a simple message notifying
            ;;   ;; weather report is not available.
            ;;   (setq ansi t)
            ;;   ;; Need a 256 color ansi library, emacs supports only basic
            ;;   ;; ansi colors as now, so replace all 38;5 foreground
            ;;   ;; specs by simple ansi sequences.
            ;;   (replace-match (pcase (match-string 1)
            ;;                    ("154" "32")
            ;;                    ("190" "31")
            ;;                    ("118" "32")
            ;;                    ("208" "37")
            ;;                    ("202" "34")
            ;;                    ("214" "35")
            ;;                    ("220" "36")
            ;;                    ("226" "33")
            ;;                    (r     r))
            ;;                  t t nil 1))
            (ansi-color-apply (buffer-string)))))
    (erase-buffer)
    (save-excursion
      (if data
          (insert data)
        ;; Probaly check error status instead (it is 52).
        (insert "Empy reply from server"))
      (forward-line -1)
      (when (and ansi ; Keep notification when no weather report.
                 (re-search-backward "^$" nil t))
        (delete-region (point) (point-max))))
    (while (re-search-forward "\\s\\" (point-at-eol) t) (replace-match ""))
    (goto-char (point-at-eol))
    (insert (format-time-string " le %d/%m/%Y à %H:%M:%S"))))

(defun wttr-weather-revert-fn (_ignore-auto _no_confirm)
  (wttr-weather-update wttr-weather-last-location))

(define-derived-mode wttr-weather-mode special-mode "wttr"
  (make-local-variable 'wttr-weather-last-location)
  (set (make-local-variable 'revert-buffer-function) 'wttr-weather-revert-fn))

#+end_src




In GNU Emacs 28.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, cairo version 1.16.0)
 of 2022-04-05 built on IPad-S340
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Linux Mint 20.2

Configured using:
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<#secure method=pgpmime mode=sign>

-- 
Thierry