Weather Widget

At this point in time, you cannot depend on the Dashboard weather widget working reliably. Dashboard is gone in macOS 10.15 (Catalina). Take advantage of the weather widget in the macOS Today view of the Notification panel.

In System Preferences : Extensions : Today panel, select Weather.

You then click on the right-most icon of the menu bar that appears as ⁝≣ and you should then click on the Today tab. The weather widget will initially appear as:

Click the green add, and enter your location as name, or zip code, and then click Done. Now, as you click the Weather widget, it will appear in minimalist, or expanded form.

If you mean the one in the Dashboard it comes and goes. It's not been working for several days.

WeatherBug has a very nice menu bar weather icon (my preferred way to check my weather). If interested, search the App Store.