When is a $66 million opening weekend a meh opening weekend? When it's a tentpole superhero movie (“Thor”), released into nearly 4,000 theaters (3,995), during the first weekend of May (prime movie real estate).

Here are the big grossers for the first weekend of May during the last few years:

• 2010: “Iron Man 2” ($128m)
• 2009: “X-Men Origins: Wolverine” ($85m)
• 2008: “Iron Man” ($98.6m)
• 2007: “Spider-Man 3” ($151.1m)

You'd have to go all the way back to 2006, and Tom Cruise's “Mission Impossible III” to find a lower opening gross, $47.7m, than the $66 million “Thor” pulled in.

I'm sure Paramount and Marvel Entertainment were hoping for an “Iron Man,” or even a “Wolverine.” Instead “Thor”'s open is closer to “Hulk” ($62m in 2003) and “Fantastic Four: Rise of the Silver Surfer” ($58m in 2007). It's the 55th biggest opening weekend ever, which ain't bad, but adjust for inflation and it falls to 101st, behind such tentpole flicks as “The Waterboy” and “Scooby Doo.” And “Hulk” and “Fantastic Four.”

So we know “Thor” won't be a $300 million movie. But can it be a $200 million movie? To do so, it would have to triple its opening weekend total, i.e., make opening weekend 33 percent of its overall gross. That's doable, but would require some strong legs. “Iron Man” did it in 2008. Its opening weekend was 31 percent of its overall gross. But “Iron Man” had great word-of-mouth and cast-iron legs.

On the plus side, “Thor” has already grossed $176 milliion overseas. Asgard's box office: n/a.

In other news, “Fast Five” dropped fast. It finished second for the weekend but dropped 62.3 percent from the previous weekend.

The thunderous totals here.

Strong arms, yes, but you lift with your legs.

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