Paul Dunne and Marc Warren both produced big finishes to sit atop a congested leaderboard after day one of the Open de España.
Warren birdied five of his last seven holes to sign for a 66 and get to six under and it looked like he would lead on his own as heavy rain moved in during the late afternoon at Centro Nacional de Golf.
The conditions proved no problem for Irishman Dunne, however, as he finished with an eagle to join the Scot on top and lead by one from a group of 11 players.
World Number Four Jon Rahm and amateur Victor Pastor delighted the home crowds at five under alongside English trio Aaron Rai, Callum Shinkwin and Jonathan Thomson, Swedish pair Alexander Björk and Henric Sturehed, Frenchman Julien Guerrier, Australian Jason Norris, Austrian Matthias Schwab and South African Erik van Rooyen.
Defending champion Andrew Johnston was then in the group at four under, with 40 players within three shots of the lead.
Warren sandwiched a bogey on the fourth with birdies on the second and fifth to turn in 35 but really came to life on the back nine. The three-time European Tour winner birdied the 12th and 13th, followed that with two pars, but then closed with three further gains to jump out into the lead.
"It was good," he said. "Finished with three birdies in a row so it kind of makes it look a little bit better.
"Overall, it was really solid tee to green. I putted really well today - pace was really good. The putts that missed I didn't leave myself much to do and the good putts always looked like they had a chance of going in.
"You know when you're out that early and it's cold and windy it's always going to be a tough start so it's important to be patient. I'm really delighted with that start."
Dunne had a birdie-bogey start and made another gain on the fifth to turn in 35. Further birdies followed on the 11th and 13th and when he holed a good putt from the fringe on the 16th, he was in contention. The best was to come on the last as the British Masters supported by Sky Sports champion put his second to six feet for a closing eagle and a share of the lead.
"I'm pretty pleased," he said. "I find the greens quite tricky to read out there, especially on the front nine, so it was nice to get a couple of putts go in on the back nine and give myself a climb up the leaderboard.
"Our front nine was quite windy and that just makes it trickier to putt than anything else. This golf course with the rough the way it is - kind of patchy - you can get away with some bad shots but it's just hard to make the five, six-footers for par if you get out of position.
"Then on the back nine the wind died a little bit but the rain came in so it was a tale of two halves. I'd rather the little bit of rain and calm conditions because it makes the greens a little more puttable for me."
Pastor began his round with an eagle on the tenth and turned in 32, with a closing bogey dropping him out of the lead, while Rahm and Thomson both had an eagle and a bogey in their rounds.
Van Rooyen and Rai both made two eagles, with Guerrier denied the overnight lead thanks to a double-bogey on the eighth.
Björk and Norris were both bogey-free, while Shinkwin, Sturehed and Schwab all had a single blemish on their cards.
Local favourites Nacho Elvira and Pedro Oriol, South African pair Trevor Fisher Jnr and Richard Sterne, German Sebastian Heisele, Dane Thorbjørn Olesen, Australian Brett Rumford and fellow Englishman Paul Waring were alongside Johnston two off the lead.