CHICAGO — There was rain. And then there was more rain. And then there were mistakes.

Sunday’s season opener was not easy on the eyes. For all the encouraging moments, there were far more head-scratchers in the 49ers’ 19-10, season-opening loss to the Chicago Bears at Soldier Field.

The Bears offense was tepid at best, consistently struggling to move the ball. But the 49ers gave them chance after unearned chance, letting their opponents hang around just long enough to keep the game close.

Eventually, they weren’t just close. After looking horrid, like one of the NFL’s clear bottom-feeders, the Bears took the lead from the 49ers at the start of the fourth quarter, as Talanoa Hufanga — who had an outstanding game with mostly linebacker duties — lost Equanimeous St. Brown in coverage for a touchdown.

It didn’t stop there.

Down just three after a missed extra point, Trey Lance, who hadn’t made many mistakes, made his worst one at a time the 49ers could not afford it.

After a huge conversion to Ross Dwelley and a few runs, Lance looked for Jauan Jennings on a key 3rd-and-5. And by looked, we mean looked.

He stared Jennings down and veteran safety Eddie Jackson read Lance’s eyes the entire time, jumping the route for a back-breaking interception.

Then the defense, which had held firm all game, allowed a touchdown to Khalil Herbert. A defensive holding by Javon Kinlaw turned a 2nd-and-11 into a first down inside the five to set that up.

On the whole, it was a performance riddled with errors.

The obvious place to start is the penalties. The quantity and timing of the 49ers’ penalties was outrageous.

They had 12 total penalties for 99 yards. Chicago? Three for 24 yards.

Among the more brutal ones, there was a Charvarius Ward holding call on former 49er Dante Pettis. Three plays later, Azeez Al-Shaair hit Justin Fields on a slide for a personal foul. Three plays after that, Fields found St. Brown for the touchdown that put the Bears ahead.

There were plenty of other moments to rue. On the first drive of the game, Deebo Samuel fumbled and turned the ball over at the Chicago 12-yard line.

The Bears’ first touchdown drive, too, should have been over, twice. Dre Greenlaw was called for a personal foul — a facemask — on a play where at least two other 49ers defenders, and Bears left tackle Braxton Jones, had David Montgomery stopped cold.

Two plays later, Fields threw what should have been an interception to former Chicago safety Tashaun Gipson Sr. It went right through Gipson’s hands.

Two plays later, the 49ers were punished. Pettis, in what now stands as a revenge game, found himself wide open as the Bears’ offensive approach of just letting Fields run around, paid dividends.

Fields bought himself enough time to see Pettis completely uncovered, for a 51-yard touchdown.

Up until that point, Fields had 19 yards passing.

And the San Francisco offense went silent in the second half, when the team was outscored 19-3, with Elijah Mitchell gone from the game.

This is not a loss that lies on Trey Lance’s shoulders, despite the brutal interception. He wasn’t stellar, but had some impressive moments, like a 3rd-and-13 first down run, a 44-yard completion to Jauan Jennings, a dart of a ball to Ray-Ray McCloud, a key conversion to Dwelley, and some impressive runs.

He neither won them, nor lost them the game. And by the fourth quarter, the swells came back. By the time Herbert ran in that touchdown to put the Bears up by nine points, the 49ers had completely lost their chance to mount a comeback.

While the field held up for most of the game, it turned into a pond late in the fourth quarter, with massive puddles popping up everywhere.

It will be a game the 49ers will want to forget, desperately, but one they’ll have to rewind, painfully, to improve on. With a projected brutal second half of the season, this was supposed to be a scheduled win. That it was not may require some soul-searching.