Clouds, winds and rain are forecast in Vigo, Europe's largest fishing port and Galicia's biggest city of 300,000, tonight.
The 500 police - four times the figure of a normal Celta Vigo league game - working at the Galician derby, where 31,000 home fans and 800 away fans are expected, will be familiar with the conditions.
Assumptions that Spain is a country of permanent sun are blown away in the country's green north west, where the Atlantic lashes against the rocky coast.
It was sunny in June during celebrations for Celta Vigo's automatic promotion back to Spain's top-flight.
They would have been bigger had Deportivo La Coruna, Celta's main rivals from the region's second biggest city of 250,000, not finished one place above them as champions. Depor, from 100 kilometres to the north, won both derby games last season and the pair meet tonight for the first time in the Primera Liga since 2007.
"The derby in the second division was a big game, but this is even bigger," said Depor coach Jose Luis Oltra.
The weather is not the only thing which has turned, with both clubs facing the tough reality of life in the top flight.
Depor won the league with 91 points, but the wins have stopped and they have triumphed in just one of their eight games since promotion - their first, back in August - and sit uncomfortably in 19th.
Depor have lost their last four matches, conceding 14 goals.
Celta have fared better, managing three wins, all of them all home, but nine points from eight games is near relegation form.
Primera Liga consolidation is the aim for both, with expectations well down on a decade ago.
In 2002-03, Deportivo, league winners in 2000, finished third with Celta one place behind, Barca a distant sixth.
Depor beat Manchester United at Old Trafford and reached the Champions League semi-finals.
Both teams have played Champions League football and featured top-class players such as Rivaldo, Juan Carlos Valeron, Roy Makaay, Aleksandr Mostovoi, Michel Salgado Salgado, Sylvinho and Diego Tristan.
Then a gradual decline set in, the Galicians unable to compete given Barca and Madrid's burgeoning commercial and television revenues.
Celta were first relegated in 2004, though they bounced back before going down again in 2007 and sliding into administration.
When Deportivo, who had their playing budgets progressively cut, followed them in 2011, Galicia was without a top-flight team for the first time in two decades, yet last season reinvigorated both clubs.
Depor made an immediate return, with two club legends among the stars.
Club captain Manuel Pablo and vice captain Valeron, both 37, are veterans from the super Depor side who are still playing in the Riazor - Europe's best-located stadium by a stunning Atlantic beach. Both expect to play tonight.
Younger charges have come through the ranks too, most notably at Celta where locally born striker Iago Aspas, 25, has spent all his life at the Balaidos and is the team's top scorer.
Aspas admits that he has no love of Depor and once celebrated Celta's Brazilian player Vagner kicking Depor star Tristan "as if it was a goal". That earned him a public reprimand from his club president, but the fans love him for it.
"We're favourites for this game," said Celta's number 10. "We're in our home with our fans."
Galicia's two biggest clubs (former first division sides such as SD Compostela have long faded, while tiny Lugo are the region's third-placed club, having risen to the second division for only the second season in their history this campaign) are both in debt, but Depor's €40 million (Dh190m) playing budget and Celta's €33 million wage bill should be enough for any sides aiming to stay up.
Celta, managed by Paco Herrera, a former assistant to Rafa Benitez at Liverpool, have made the better start.
Not for the first time, Depor aim to spoil it by winning the Galician derby.
Espanyol v Malaga 6pm
Betis v Valencia 8pm
Celta Vigo v Deportivo 10pm
Rayo v Barcelona midnight
R Zaragoza v Sevilla 3pm
Levante v Granada 7pm
Athletic v Getafe 8.50pm
Atletico v Osasuna 10.45pm
Mallorca v Real Madrid 12.30am (Monday)
V'dolid v Sociedad 12.30am (Tuesday)
Ligue 1 table
Team P W D L GD P
Barcelona 8 7 1 0 13 22
Atletico 8 7 1 0 11 22
Malaga 8 5 2 1 8 17
Real Madrid 8 4 2 2 9 14
Sevilla 8 4 2 2 2 14
Betis 8 4 1 3 -1 13
Levante 8 4 1 3 -4 13
Mallorca 8 3 2 3 1 11
Valencia 8 3 2 3 0 11
Valladolid 8 3 1 4 3 10
Getafe 8 3 1 4 -3 10
Rayo 8 3 1 4 -6 10
Celta Vigo 8 3 0 5 -1 9
R Zaragoza 8 3 0 5 -3 9
R Sociedad 8 3 0 5 -4 9
Granada 8 2 2 4 -5 8
Athletic 8 2 2 4 -6 8
Deportivo 8 1 3 4 -6 6
Espanyol 8 1 2 5 -4 5
Osasuna 8 1 2 5 -4 5