After about 9 years I have a solution. I hope it is still valid.
The solution will not modify the lock screen. It will run over it.
I posted a question in another forum to find a way to run weather on Windows lock screen. I found a solution using rainmeter and a few others that is simple. During my search for the solution I saw this question and decided to update it once I have a solution.
This is the link to the solution:
https://windowsforum.com/threads/run-programs-on-lockscreen-of-win7-8-1.250494/
I am pasting the solution here below from that same link.
-------------------------------------------------------------------------------------------------------
The next post is the safer way to run live wallpaper on the lock screen (because IrfanView gives access to disk files.) do the same thing but it is more complicated.
I found a solution by using the following method.
It takes 3 programs to get it to work as soon as the Screen is locked. The same method works on both Win 7 and 8.1. Tested and works on Windows 10 as well
The three programs are listed here below with links to download them. There is one more program mentioned for running live wallpaper on LockScreen.
All programs are free
RunSaver
https://runsaver.de.softonic.com/?ex=TRAF-469.1
Rainmeter
Download the final release:
https://www.rainmeter.net/
Nircmd (At the bottom of the page. Not the 64 bit one.)
https://www.nirsoft.net/utils/nircmd.html
-----------------------------
Runsaver: is to run any program when screensaver is triggered. (This will replace any screensaver you might be using).
Rainmeter: is an amazing program with plenty of features. It works by installing skins which creates a background with many components. The background can also have some or all components on top of all windows. It can also run components from many different skins at the same time without needing any editing. If it will be used then check YouTube videos and use their Forum (I get response within 1hr on Forums. They have very good support).
Irfanview : is a media viewer and should be set as the default tool to run Gif files (if another one is not already in use).
-----------------------------
As for running weather on lockscreen as soon as it is locked then use the following method:
Extract Runsaver and add the two files called runsaver.exe and runsaver.scr to windows\system32 folder and for 64bit windows also add it to SysWOW64 folder.
To Change the program that will run on the screensaver then open the Windows screensaver tool and click on settings and add the path to the program that will run on screensaver.
Runsaver will create INI file in the both directories which will be identical and no need to worry about them. (I had an issue on win 8.1 and where it did not update the changed program.) If there is an issue then just search for all the runsaver.ini files under the windows directory and delete them, then add the program that you want again. (There will be more than 2 Runsaver.ini because windows will add the runsaver files to more directories. If not found then search the entire C directory for Runsaver.ini)
To use enable runsaver so that it runs the program when screensaver starts just choose runsaver as the windows screensaver.
To exit screen saver after it starts just press on Ctrl+Alt+Del. Mouse or other keyboard buttons do not seem to do so.
Because Runsaver takes over the entire screen you will need to create everything including the background if it is not taking up the entire area with Rainmeter.
After installing Rainmeter, create all the things you want to show on the lock screen including the clock. (I was searching for a way to display clock on lock screen like it is on Win 8, 10 and many also searched for it in forums. The one available is a tool that does not look good as it takes over the entire lock screen and works with a strange timer setting).
The below link is for the latest updates for the weather that work. Others on the web are old and do not work. Not all will provide the needed information. Some of them can be made to be glass and transparent.
Weather Skins - Rainmeter Forums
Rainmeter works by using INI files for quick editing. They are edited with the notepad program. For safety on the lockscreen you will need to disable right click by using the following code.
Just under
[Rainmeter]
add
RightMouseUpAction=[]
in the INI file and save it.
To disable setting then just delete the INI settings file.
There are options for each component to be at the bottom or at the top of others or on top of all windows. This will need to be done if the components are not showing up. (They might be behind others).
To run live wallpaper on lock screen then it is recommended to use GIF files because videos will run with complete player control (Which is a security risk).
I use IrfanView as the default GIF player. It has options to run immediately in fullscreen and will show directory on the top left corner by text which can be removed from the features. If used in fullscreen then it can exit with the esc button.
Choose the GIF file in the Runsaver application path.
Some programs will not run on runsaver if they are already running on the computer. So close the program to work on the lock screen if there is an issue.
Then you can just proceed with the login after exiting the Runsaver screensaver.
Only Rainmeter needs to be allowed through the firewall for live weather updates.
Sometimes it might be needed to install the beta version. I recently had to use it because of some issues with weather. However, any issue you might be facing just request for support on the forum.
To run the screen saver as soon as the screen is locked regardless of the delay assigned then create the batch file. To create a batch file then open a text file and change the extension from ".txt" to ".bat". To edit the batch file just right click on it and choose edit.
Enter the following commands in the batch file and save it.
-----------------
@echo OFF
Timeout /T 6
Nircmd.exe Screensaver
Exit
----------------
The number after Timeout is the number of seconds.
Then create a task in task scheduler (Default program in Windows). Name it something related to this guide.
On the triggers tab, just use “On Workstation lock” from the drop down menu.
On the actions tab, choose the batch file that was created.
On the conditions tab, uncheck ”Start the task only if the computer is on AC power” for laptops and tablets.
After boot up the screen saver runs within a few moments (Even before login) and Crtl+Alt=Del will not exit it. Press on Crtl + Mouse right click then go to Rainmeter then Exit.
