A wayward tropical storm, a flood advisory and rain at dusk set a gloomy tableau as Heat fans arrived downtown for Game 1 of the NBA Finals here Thursday night.

Inside the basketball arena, the outlook did not improve.

You don’t need a weatherman to tell which way the win goes — you just listen to the crowd — and the one spilling into downtown Miami after this game slumped and moaned and dragged. It was near midnight. The sun could’ve been shining and birds could’ve been chirping. It wouldn’t have mattered.

The Heat had lost.

The climb to a second consecutive championship got steeper, fast.

Miami’s two previous NBA titles, in 2006 and last season, happened to both come after a Game 1 loss in The Finals, so that would qualify as the good news today to the most extremely superstitious among Heat fans.

To everybody else, not so much.

The Heat’s 92-88 opening loss to the San Antonio Spurs means Miami now faces a Sunday Game 2 back here that suddenly will be draped in desperation, an all-but-must-win for the Heat with three straight games in San Antonio following that one.

Miami led by three entering the fourth quarter but failed to hold on against a smothering San Antonio defense and a Spurs offense that tied an NBA Finals record with a mere four turnovers.

Losing coach Erik Spoelstra referred to “offensive inefficiency going down the stretch, most of the fourth quarter.” He referred to “three or four possessions where we didn’t get organized and the ball didn’t go where we wanted.” He said, “Our turnovers in the fourth quarter really hurt us.”

Those are kind ways of saying his team played badly when the stakes were highest — that his team let a victory slip away.

What made the outcome even tougher to take for Heat fans is that Miami narrowly outshot the Spurs, had more rebounds, and got a triple-double from league MVP LeBron James, who had 18 points, 18 rebounds and 10 assists.

Dwyane Wade contributed 17 points, but only four after halftime.

Chris Bosh added 13 points.

The combined 48 points by the Big 3 is below their combined regular-season averages, and will have to improve as the series moves on.

Nobody should doubt that the Heat will bounce back to make this a long series of the type NBA Commissioner David Stern had in mind when, before the game, he called this “probably the most anticipated Finals in, who knows, 30 years.”

Dismiss some of that to a commissioner simply selling his product, although the game that followed might have justified his optimism a bit.

It was a game that swung each way, then back, with neither team ever ahead by double figures.

There is a lot to like about this Finals.

It is a contrast of Present and Past, Now vs. Nostalgia.

Miami, present and now, seeking its second consecutive title in what would be a legitimate claim to the makings of a modern dynasty. And San Antonio, past and nostalgia, in its first Finals since 2007, its aging core looking for one last hurrah.

It also is a duel of “Big 3’s” — the Heat’s James/Wade/Bosh troika vs. the Spurs’ Tim Duncan, Tony Parker and Manu Ginobili.

A certain mystery also gave the buildup to Game 1 an unusual element.

The teams met in Miami this season and San Antonio left its star players back home, drawing a fine from the league. The Heat later played in San Antonio and rested LeBron and D-Wade as apparent payback.

That meant Thursday night marked the first time since March 14, 2011, that both teams had faced each other full-strength, Big 3 vs. Big 3.

This series looks like it will be fun in a way this Heat postseason has not been in the three previous series.

The first, vs. Milwaukee, didn’t even feel like the playoffs at all, so inferior were the Bucks.

The next two, vs. Chicago and then Indiana, were defense-minded, half-court-oriented grudge matches. They were full of elbows and technical fouls. They were not so full of anything you’d call artistic play.

But this Finals, based on early evidence, finds two teams wanting to run, wanting wide-open attacks.

Now we see the Heat’s resilience.

We have seen it before.

We saw it last year when trailing in three consecutive playoff series did not prevent a championship parade.

We saw it just a few days ago when Miami was up to a Game 7 challenge in the conference finals.

“We have been through a lot and showed resolve and toughness,” said Spoelstra.

They’d better show it again.

Now.