a hurricane warning

Some branches of the government monitor the weather, and release warnings when dangerous weather is likely to occur. If you watch or read the news, you might find out about:

tornado warnings

tsunami warnings

flash flood warnings

By the way, "hurricanes" are big storms that happen in the Atlantic Ocean. In the Pacific Ocean, they're called typhoons.

(something) is in effect

The example above says that a hurricane warning "is in effect". That means that there is currently an active hurricane warning.

Other things that can be "in effect" are laws, policies, rules, etc.:

There's a new "no-bag" policy in effect at Spartan Stadium. It's supposed to prevent people bringing weapons into the stadium.

Several states have laws in effect banning cell phone usage while driving.

When a rule, law, or warning first begins to be in effect, you say that it was "put into effect":

A ban on indoor smoking was put into effect in New York in 2003.

(something is happening) throughout (a location)

If something happens "in" Delaware, that might mean that it's only in one specific city or one part of the state. But something that happens "throughout" Delaware is all over the state, or in several different locations spread across the state.

Things can happen "throughout" a country, a state, a region, a company, an industry, a building, etc. You can also talk about things that happen "throughout" a time period:

England and France repeatedly warred with each other throughout the Middle Ages.