HOLLYWOOD — The first thing that happens at a Hollywood High football practice in August is that a man with a small gray instrument walks to the middle of the field, holds it above his head for four minutes, and writes a number on a clipboard.

On Wednesday the number was 82.1, which meant practice as planned. On Thursday it was 89.4, which meant a modified session with mandatory breaks every fifteen minutes and no conditioning at the end. If it had read above 92, there would have been no practice, and the coaching staff would have spent two hours in a classroom with a projector instead.

“Nobody had one of these when I played,” said Delroy Fenwick, in his sixth season as the Sheiks’ head coach, holding up the wet-bulb globe thermometer that section rules now require on the field before every August practice. “In 1994 we did two-a-days in full pads in this exact heat and the water break was when the coach decided you’d earned it. Two kids in this state died the summer I was a sophomore. That’s why I own this thing, and I’m not sentimental about the old way.”

Preseason practice opened last week across the section under an acclimatization schedule that has been in place, in one form or another, for more than a decade and that gets stricter roughly every time a study is published. The first five days are helmets only, no shoulder pads, one practice per day, and no contact of any kind. Days six through nine add shoulder pads. Full pads and any live contact wait until day ten. Consecutive two-a-days are prohibited outright, and a two-a-day, when it eventually happens, must be followed by a single-practice day.

At Hollywood, all of it now happens at six in the morning.

That is a change of the coach’s own making, adopted last summer after the school’s afternoon field measured 94 on the instrument for four consecutive days and the team lost most of a week. The morning session runs 6 to 8:15. Players arrive between 5:30 and 5:45. A parent volunteer runs a table with water, ice towels and, at Fenwick’s insistence, a scale, because the surest early sign of a player in trouble is a body-weight difference between the start and end of a session.

“Two percent is a conversation. Three percent, you’re done for the day and you’re drinking in front of me,” Fenwick said. “The kids hate the scale more than they hate the running.”

The roster is one of the more experienced Hollywood has had. Xavier Poole, the senior quarterback who threw for better than two thousand yards last season, spent the summer, by his coach’s account, mostly trying to get bigger, and by his own account trying to get bigger while working a summer job at a market on Western.

“Coach wants two hundred and five. I’m one ninety-six,” Poole said, standing in the grass at 8:20 with his helmet off and his shirt soaked. “The six-in-the-morning thing is honestly better. I was falling asleep in the afternoon anyway. I just wish it didn’t mean going to bed at nine like a child.”

The crosstown preseason game against John Marshall — the series older than either coaching staff, played for a foot of dented brass whose provenance the two schools have never agreed on — is scheduled for the end of the month. Fenwick refused to discuss it in any detail whatsoever, on the grounds that it is August 2, and then discussed it for six minutes.

What worries him about the schedule is not the heat rules, which he supports without reservation, but what they cost a program with no lights and one field. Hollywood shares its field with the girls’ program, the band and, on two afternoons, a youth league; a mandatory single practice per day in the first nine days means the field’s morning window is the only window, and the morning window is also when the district’s summer maintenance crews want it.

Twice last week they had it at the same time. Both times the crew waited, which Fenwick made a point of mentioning, and one of them ran the sideline hose for the water table.

By 8:30 the field was empty, the instrument was back in its case, and the number on the clipboard — 89.4 — had been entered into a log that the section can ask to see at any time. Practice Friday was at six.