I tried the Weather Channel app, but it only notifies advisories and warnings, as opposed to temperatures and forecasts.
Here's what I managed to put together:
1) Go to wunderground.com on a desktop or laptop browser (NOT on your iPad or other iOS device), search for your area (zipcode is probably the best way), and click search to bring up the page.
2) Click the down arrow just to the left of the small orange RSS icon (this doesn't seem to work on iOS), copy (not click) the "Download iCal" link, and e-mail it to an e-mail account that's accessible on your iOS device.
3) Get on your iPad, copy the iCal link from wunderground.com.
4) Go to Settings > Mail, Contacts, Calendars and click "Add Account", then click "Other", then "Add Subscribed Calendar". Paste the link next to "Server", click the "Next" button, and then click "Save" when the information is verified.
This will subscribe to the forecast for your area in the iPad's calendar. Next, you want to make sure that it updates regularly, and displays in your notification center.
5) Go to Settings > Mail, Contacts, Calendars and click "Fetch New Data". Make sure that either Push is set to ON, or Fetch is set to one of the following settings: "Every 15 Minutes" / "Every 30 Minutes" / "Hourly".
6) Click on "Advanced", and make sure the subscribed calendar is set to "Fetch", or "Push" if you have Push set to ON.
7) Go to Settings > Notifications and click on "Calendar" and make sure Notification Center is set to "ON". If you set "Show" to "5 items", Notification Center will always display the forecast for today and tomorrow.
That gets you an updated forecast in your notification center, via your calendar.
Next, you're going to set up an RSS feed showing the current temperature conditions in Notification Center.
8) Go back to the wunderground.com site, on your iPad this time, and go the page for your area (as you did before).
9) This time, click and hold on the RSS link, and copy the link.
10) Go to Google Reader ( http://www.google.com/reader/ - set up an account if needed), click "Subscribe", paste the RSS link you just copied in, and click the Add button.
11) Download and open the Push Reader app (it's made for iPhone/iPod Touch, but will work on the iPad). Set up the link to your Google Reader account according to the instructions.
12) Under Push Config in the app, make sure the weather feed is set to ON. Adding the keyword "Condition" will make sure you only get the current conditions. You may want to add the keywords "Advisory" and "Warning", as well.
13) Get out of the Push Reader App, go to Settings > Notifications and make sure "Notification Center" is set to ON. Set Show to the number of items you want to see in Notification Center.
If this is done right, in Notification Center, Push Reader will display the current conditions, and Calendar will show the forecast for your area. They'll also update regularly and automatically.
For whatever reason, wunderground.com sets up their RSS feed and iCal feeds are set up differently, and this is the simplest way to get the current conditions along with the forecast for your area.
The reason I chose wunderground.com in particular is that both feeds mention the important details in the feed title, so they show up in Notification Center. Too many other weather feeds simply have titles such as "YOUR LOCAL FORECAST" or "LOCAL CONDITIONS", which are useless for viewing in Notification Center.
