You can set it to update as often as you'd like. Alerts are storm watches, wind gusts (in my area), etc. Visual alert is when the big turns red as opposed to a audio alert. Hope this helps...
Posted from my CrackBerry at wapforums.crackberry.com
Its prolly best free weather app for blackberrys. Have mine setup for every 30 min updates. Just click bb button and ADD LOCATION. Not sure how many locations u can add but I have 2. Also it has a feature where it will use GPS to find ur location and get temp for u. But it only worked once for me and after that kept giving me Canadian locations. Not sure why. Btw, when u see the ladyBug , just click on it and it will update the temp on the icon.