Linux

Sounds like Emacs' orgmode could be useful.

Looked at this it the past but never ended up using it myself. https://taskwarrior.org/

Check out CalCurse, I use it for exactly this purpose. It's primarily a curses tui application but it can also print itineraries and todos to the console.

scientiist/todo is pretty good. https://github.com/scientiist/todo

Not sure if you've looked at remind (this is an older article, but still relevant). It may take a little to get into, but it does a fantastic job of organize calendar stuff. As far as teminal init, I have something like

remind -cl+1 -w`expr $(tput cols) - 10` /home/user/.reminders

So I have the current weeks events printed across the top of the terminal. Remind can also schedules pop-up reminders for upcoming events. The only awful thing about remind is it's a pain in the ass searching for it. It does have an active mailing list where you can get quick answers to just about any question, no matter how complicated or simple.

For todos, I've tried both todo.txt and taskwarrior. And a few others if I'm being honest. I've never been able to stick with a todo app, so I can't offer much advice.

Weather, I use the same as you. I have family all over the world, so I set up aliases based on their names that show me the time as well as the weather. For example:

[\ #1]  Bob
tokyo: ⛅️  +82°F
Sunday 05:24 AM
 [user@home\ :6|~]
[\ #2]  type Bob
Bob is aliased to `curl wttr.in/tokyo?format=3;TZ=Asia/Tokyo date "+%A %I:%M %p" '

I'm not much help putting it all together, but I think you are on the right track for you. There are tricks to getting multi-line outputs to be side by side, I can give you some help there if you want, but you're really like 95% there.

For calendar, I use khal, which offers a TUI (ikhal command) and a non-captive UI that can print a simple list like you might want (khal command). It supports multiple calendars, ical, recurring events, etc. Since it support ical, you can add locations, times, dates, alarms, pretty much anything you want. No database required, each event is saved into a seperate ical file (easy to import into another program, if you wanna switch someday).

I also use todoman for to-do lists, which is pretty similar to khal in terms of interface — having both a captive TUI and a non-captive UI.

I realize this doesn’t interest you, but as a side-note: Both of these use portable file-formats that can be synced with any pretty much any calendar-syncing service using vdirsyncer, which I use to sync my events and todo-lists and address book using Posteo.