What you're probably noticing
You pull up your own site on your phone while you're waiting in line at a coffee shop on the Plaza, and it looks fine. But that's the easy version. You're on good wifi, you already know where the menu button is, and you're not trying to do anything urgent. That's not how most of your actual customers meet your site.
A real Kansas City customer is more likely checking your hours from a parking garage downtown with one bar of signal, or looking up your plumbing company at 7am during an ice storm when half the region's data networks are slammed because everyone else is doing the same thing. The test that matters isn't whether the site opens. It's whether it works under conditions your customers actually have.
Test it the way the weather tests it
Kansas City runs hot, humid summers and genuinely cold winters, and both do something to how people use their phones. In August, people are outside less, glancing at screens quickly in air conditioning or shade, often with sweaty fingers that make small tap targets miss. In January, during an ice event or a deep freeze, people are in their cars with gloves on, trying to get information fast before they lose patience or their hands get cold.
Try tapping your own buttons with a glove on. Try reading your own text in direct sunlight by stepping outside with your phone at midday. If your call-to-action button is a thin line of text, or your contrast is too soft, you'll find out in about ten seconds what a customer on Ward Parkway finds out when they're trying to call you from their car.
More on this from Reading List Testing Your Own Site The Way A Kansas City Customer Meets It.
Test it on the roads people actually drive
A lot of Kansas City business happens via phone while someone is moving between places, not sitting at a desk. Someone driving up I-35 from Overland Park, or cutting across on 435, loses signal in stretches and gets spotty 4G in others. If your site depends on a fast, steady connection to load images or maps, it will stutter exactly when someone is trying to find your Westport location before they miss the exit.
You can test this yourself without any tools. Turn on airplane mode, then flip on wifi with a slow public network, or just drive through an area you know has bad signal and try loading your own site. If it hangs for more than a few seconds or the layout jumps around while things load, that's a real problem, not a hypothetical one.
Test it the way someone actually taps and reads
Thumbs are not mice. Most people hold a phone in one hand and tap with a thumb, which means buttons near the top corners or crammed together down the middle are hard to hit reliably. Sit down with your own site and try to complete the thing you want a customer to do, book a table, request a quote, call you, using only your thumb, one-handed, without zooming in.
Pay attention to whether you have to pinch and zoom to read anything. A lot of older Kansas City small business sites were built for desktop screens and then just shrunk down, which leaves text too small to read without effort. If you find yourself squinting or zooming, so will your customers, and most of them will just leave rather than fight with it.
What you can fix yourself versus what needs real help
Some things are within reach for any business owner willing to spend an afternoon on it. You can check that your phone number is a tappable link instead of plain text. You can check that your address opens directly into a maps app instead of making someone copy and paste it. You can check that your hours are visible without scrolling, since that's one of the most common things people look up on the go.
Where it gets harder is anything structural: pages that load slowly because of oversized images, layouts that break or overlap on certain phone models, forms that don't work right on touchscreens, or a site that was built years ago on an older platform that was never designed with phones in mind. If fixing one thing seems to break another, or if you don't know why a page takes eight seconds to load, that's the point where it's worth bringing in someone who builds mobile sites for a living rather than tinkering further on your own.