Have you installed Lockscreen Info? If not, do so. Download the Lockscreen Weather plug in and it will pull in the weather and update it at times you select (ie, every minute, 15 minutes, etc). It will also show the five day forecast, which you can hide by tapping the current weather icon. Be sure and also download and install Hide Clock so you won't have two clocks on the screen.
Lockscreen Info will give you more options too. You can have your calendar events show on the screen for the next couple of days, ToDos from Appigo's ToDo will show, missed phone calls and SMS messages too can all be shown as well as RSS news headlines.