One neat feature found in the "Leo" TouchFLO aka Sense 2.5 is the ability to set the update frequency of the weather tab.
For folks using Sense 2.1 aka the "Weather clock" version, this option does not exist--you only have "update automatically" which seems to go about every 2-3 hours.
Seeing as Windows Mobile fans are united in their desire to tweak and set every feature on their Windows phone, it was no shock that people were clamoring "fix it, fix it, fix it, fix it!" (to quote philosopher Philip J. Fry).
Well, it's been fixed. Seems XDA member Notaliberal found the registry entries that control the frequency:
Create this DWord entry in the following key:
Dword Name: Weather.AutoDownloadInterval
DWord Value: 30 (Decimal)
Change the value to whatever time you want in minutes. Reboot. Voila!
Update: like a lot hacks, this sometimes works and sometimes doesn't . Seems it is depenedent on what software version you are running and other unidentified factors. So while this works for many, for some it won't.