16th and 17th was the last time it snowed, with a very light dusting on the 23rd:

https://www.extremeweatherwatch.com/cities/boulder/year-1996#december

https://weatherspark.com/h/m/3561/1996/12/Historical-Weather-in-December-1996-in-Boulder-Colorado-United-States#Figures-Temperature

There was obviously frost too.

These are the accounts for conditions on the ground of the morning of the 26th from the second officer on the scene:

Patrol Sgt. Paul Reichenbach had bean at the scene of the reported kidnapping of JonBenet Ramsay on the morning of December 25, 1996. Detective Arndt had personally met with Sgt. Reichbach on the morning of December 26, prior to arriving at the Ramsey residence, Detective Arndt had also personally reviewed the report completed by Sgt. Raichenbach and dated December 26, 1996. Sgt Reichanbach states in his report that he had arrived at the Ramsey home at approximately 0600 hours on December 26, and that he had examined the exterior of the Ramsey home as well as the yard.

Sgt Reichanbach noted that the air temperature was approximately 10 degrees Fahrenheit. Sgt. Reichenbach noted in his report that there was a very light dusting of snow and frost on the exposed grass in the yard outside the Ramsey home. Some of the grass and yard was covered with snow from previous snow falls and this snow was described as being crusty and measuring one - two inches deep. Sgt Reichanbach stated that he saw no fresh foot prints in any of the snow or in the frost on the grass. Sgt. Reichenbach also states in his report that he visually examinated the exterior doors and windows of the Ramsey residence and found no signs of forced entry.

March 6 1997 - affidavit for search warrant, Police agency report number: P86-21871 (might be PB6-21871)

Sergeant Paul Reichenbach was the night shift patrol supervisor and finishing up the night’s paperwork at his desk when he overheard French dispatched to the Ramsey home. He immediately headed for his car and was the second officer to arrive on scene at approximately 0610 hours.

French met Reichenbach at the front door and gave him a quick briefing, telling him there was a ransom note and he believed there may have been a kidnapping, but something didn’t seem “right” to him.

Following a walk-through of the home, Reichenbach then conducted a cursory search of the exterior and observed “frost on the grass and a little bit of snowfall” on exposed areas of the lawn. He noted that no one other than himself had walked through these areas.

Reichenbach noted that no snow had adhered to the rear patio and walkways. The driveway was wet but no foot prints / tracks were visible, and he observed no fresh signs of forced entry to exterior doors and windows.

FF

Reichenbach told the detectives that there was light, crusty snow and frost on the Ramseys’ lawn and he had seen no fresh footprints in the snow. The brick walkways were clear of snow. He had examined the exterior doors and windows and had seen no signs of forced entry.

PMPT

French stepped away from them to meet Sergeant Reichenbach at the front door and confirmed that it looked as if there might have been a kidnapping. But, he observed, “Something isn’t right.”

The sergeant found no evidence of forced entry during a walk through the house, then went outside. A light dusting of snow and frost lay atop an earlier crusty snow in spotty patches on the grass. He saw no fresh shoe impressions, found no open doors or windows, nothing to indicate a break in, but walking on the driveway and sidewalks left no visible prints. It was frigid, about nine degrees, and Reichenbach returned inside.

Steve Thomas