Their instincts can be beyond explanation sometimes.
At about this time twenty years ago I'd been recently adopted by a pair of "catolescents," a brother and sister who I named "Puppy" and "Weasie." As most if not all of you know, Puppy unfortunately vanished forever in March of '93 but Weasie brightened my existence all the way until January of last year. During the brief interval they were both with me, they didn't exactly save my life on two occasions but were a big help. The first incident happened one evening when the doorbell rang. Before I'd reached the entry hall they were already in front of the door. Their meows and body language told me to not open the door without checking first. When I looked through the peephole I saw someone standing there with a clipboard. He was obviously there to conduct a survey or, more likely, to try and browbeat me into making a contribution to some cause or other. Snickering, I whispered "Thanks for the warning, kitties" and we all crept away from the door. The solicitor was none the wiser and went on his way. Not long after that, we were in the midst of a cold snap when - soon after I'd settled into bed under many layers of covers - Weasie and Puppy jumped onto the bed and ran toward my head "talking" my ear off. Only after I'd hauled myself to the floor to see what was the matter did they quiet down. It instantly dawned on me that the air was colder than it should've been, no matter that we inhabited a century-old building with drafts galore. So I trudged to the basement and discovered that the pilot light in our furnace had shut down. Within the hour a technician from the gas company had restored our heat and we were cozy from then on. Never have I been able to fathom how those felines knew that I should be spared from some fundraising sales pitch, or be alerted to the furnace's not working.
Fast-forward well into the "aughts." As I made z's one weekday morning in July at dawn, Weasie started frantically meowing a blue streak which didn't let up after I opened my eyes. A smoke alarm next door was shrieking away. In our urban neighborhood, alarms' sounding off for no good reason is part of the "sonic wallpaper." It's like living close to railroad tracks in that you hardly notice the noise nuisance after a while. Annoyed at being roused early, I humored my hyper cat by opening the shade of the window facing the townhouse whence the alarm was going off. No fire, no smoke, no suspicious smells. I groaned and lay back down, but Weasie kept on vocalizing. She moved to the bedroom doorway and looked in my direction as if to summon me to follow her. In the hope of getting some sleep before having to awaken again for work, I heeded her command and walked to the front of the house. Two fire engines, which were putting on their full light show, were parked on the street. "Weasie, they're here to disconnect the false alarm. See? There's nothing to worry about. Let's go." Weasie assented but only grudgingly. Later that day I saw the owner of the place and commiserated with her about the rude awakening. She was quick to correct me when I kvetched about the smoke alarm: "Oh, no, that was no false alarm." A boiler valve had been left closed by a contractor after repair work on the water heater was done. Despite its being summertime the system was set up so that the furnace stayed operating to enable the water heater to function. What had waked us up was a HEAT detector. And if the fire department hadn't responded there was a serious chance that there would've been an explosion - an explosion which would've set Weasie's and my home ablaze in short order.
Here again there's no answer to the question, HOW THE H--- DID SHE KNOW THERE WAS A PROBLEM???