Temp screening can be effective, but only partially - it only tells you if someone has a high temp, which is not always an indicator of whether they're sick, and even when a person is sick, they don't always have COVID-19. Also, because of the 1-14 day incubation period, someone who is infected can be contagious for days before they actually get sick and develop a fever. So altogether, the temp thing is only marginally useful at finding and weeding out COVID-19 patients. Of course, all of this goes out the window if someone's normal temp averages around 96.2, and they test out at 98.2 - that's a fever, but because the person normally runs a little cool, their elevated temp still falls close to or below the average. (NOTE: Out of curiosity I took my temp just now - not long after a good hot lunch and spending the morning vacuuming my apartment, and I'm at 96.2, right now.)

On the other hand, it also comes with some significant potential for disaster, particularly when administered by non-medically-trained personnel like airport screeners. If a nurse or doctor checks your temp and it's above 98.6f/37c, they'll check a few other things, ask a few questions, and most importantly, they'll understand that 98.6f/37c is the AVERAGE human body temp, and that half the human race will be above and half the human race will be below at any given moment. But a screener, being an untrained ordinary person, will likely use the average as some kind of absolute, disrupting travel plans for people who have just entered a terminal from a hot environment, run through the airport because they're late, eaten a large meal, are wearing outerwear because they just entered from a cold environment, or simply happen to be a that temp at that exact moment in their daily activities.

Lest you think that I'm only concerned with inconvenience or with piddling issues like civil rights, let's also remember the human propensity toward blind panic, especially in an environment that is already charged with nervousness and phobia as air travel. Someone gets a high temp warning in an airport security line, how will the people around them react? Screams? Stampedes? Police detainment? Remember the 2016 incident at JFK when the airport was locked down for hours when panicky people mistook cheers over Usain Bolt's Olympic victor for gunshots. And there have been many other terminal dumps and security scares over the years prompted by innocuous incidents, where no actual threat was ever found.
https://abc7ny.com/jfk-airport-scare...-fire/1470552/

I'm fine with temp screening being one method to prevent the spread of SARS-CoV-2, but my biggest concern with any sort of health screening is that it be done only by trained, experienced medical professionals whose judgement can be trusted, rather than the average minimum-wage airport screener whose last job involved checking the temp on the deep fryers at McDonald's.