Welcome to Android Forums, Caz!
Most likely you deleted a weather widget inadvertently. If you long-press a blank area on a home screen (touch and hold for two seconds or longer) you will get a menu to add items to the screen. Choose widgets and see if the weather widget you are looking for is there. Be advised that many of them require more space than an app shortcut, so if there is not enough room nothing may happen, or it will tell you there's is not enough room.