The 28 mph figure, and what it actually means
Most mobile elevating work platforms are rated for outdoor use up to roughly 28 mph wind speed, though the exact figure is on the machine's own data plate and some units are lower. Indoor-rated machines are rated for no wind at all.
The limit applies to the GUST, not the average. An anemometer reading of 20 mph with gusts to 32 means the machine is over its limit, and a platform at 60 ft is in considerably more wind than the person reading the gauge at ground level.
Carrying anything with surface area, whether a sheet of ply, a panel or a sign, effectively lowers the limit, because the load becomes a sail.
Where in Texas this actually bites
Lubbock and Amarillo see sustained High Plains wind rather than occasional gusts, which means planning the high-reach part of the job around the forecast rather than reacting to it. El Paso gets strong spring afternoons and dust storms that stop work outright.
Dallas and Fort Worth get convective wind ahead of storm lines: often a clear morning and an unusable afternoon. Corpus Christi runs a steady onshore breeze that can sit near the limit all day without ever looking like weather.
Houston is the exception: heat and humidity are the constraint there far more often than wind is.
What heat does to the machine
Diesel engines lose performance in extreme heat and hydraulic oil thins, which shows up as slower boom function on the worst afternoons. Radiators and filters clog faster in dusty conditions, and a machine on a long hire in West Texas needs the filters watched.
Battery machines lose runtime in heat and take longer to recharge. If a plated electric scissor lift is doing a full shift through a Texas August, plan a charge point in shade and expect less out of the pack than the spec sheet suggests.