Hard Rain (1998)

It's Die Hard...
in a flood. To be precise: a flooded town.

Is the main character an average Joe?
He just a simple armored truck driver.

Sidekick?
No, he does meet some townsfolk who could be his sidekick but nobody comes to fill that position.

Any personal problems?
He just saw his colleague and uncle Charlie being shot dead in front of him and it turns out he was working with the bad guys also. He had seen better days.

Is the lead character there by coincidence?
His truck was the target and he was just doing his job. So no.

Are there any friends or family in danger?
The only relative in the movie gets shot dead in the beginning, he does care for a woman (Minnie Driver) in the movie who serves as a love interest and has to be saved from time to time.

What's at stake and why aren't the authorities doing anything?
An armored truck full of Money. It was just supposed to be a simple heist but the flood and the persistence of one man made it more of a man chase. The authorities are on their way but it takes a while before the national guard can do anything. There is some local law enforcement but the sheriff turns out to be corrupt and tries to take the money.

Any charismatic villains?
We have Morgan Freeman and they don't get more charismatic than him. As a bonus we get Randy Quaid as the sheriff who decides that he has the right to an early retirement.

Is it any good?
This is one of those movies like Cliffhanger that stray further from the template which makes it automatically better than a lot of other entries listed here. There are some nice action sequences and overall it's a fun movie, but nothing groundbreaking. It was one of the last high profile movies of Christian Slater who would not much later pop up in Uwe Boll Movies and DTV-sequels like Hollow Man II