\documentclass[a4paper,11pt]{letter}
\usepackage[left=30mm,right=30mm,top=45mm,bottom=35mm]{geometry}
\usepackage[season=winter,weekday=friday,label={Winter correspondence}]{seasonalletters}
\signature{Alex}
\date{5 November 2026}
\begin{document}
\SeasonalReset
\begin{letter}{Morgan\\12 Example Street\\Example Town}
\opening{Dear Morgan,}
The standard letter class still controls the address, greeting, date, and
signature. Seasonal Letters adds decoration behind the page without replacing
those commands.

Its vector artwork needs no image downloads. The package can therefore be
shared as a small collection of source files with an ordinary LaTeX document.
\closing{With best wishes,}
\end{letter}
\end{document}