Spend any time around people who take backyard weather seriously and you notice something: they obsess over placement far more than over which brand they bought. That is because the most expensive instrument in the world will produce nonsense if it is mounted in the wrong spot. Almost all bad home weather data comes down to a handful of avoidable mistakes, and none of them require new equipment to fix.
The biggest by far is putting a thermometer in the sun. Air temperature is, by definition, measured in the shade, because a sensor in direct sunlight reads the heat of the sunlight rather than the temperature of the air, and the error can be ten degrees or more. Official stations shield their sensors inside a white louvred screen for exactly this reason. If your temperature always reads high in the afternoon, this is almost certainly why.
The second mistake is mounting a thermometer or weather station against a wall, especially a brick or stone one. Walls soak up heat all day and radiate it back for hours, so a sensor bolted to a sunny wall is reading the building, not the sky. The same logic ruins readings placed above patios, driveways and decking, all of which store and release heat.
The third is putting an anemometer too low or too sheltered. Wind speed is measured at ten metres above open ground for a reason; down at fence height, every tree, hedge and shed slows and deflects the airflow, so your readings come out far too low and erratic. You do not need a ten-metre mast at home, but you do need the clearest, highest, most open spot you can manage, away from the wind shadow of the house.
The fourth is siting a rain gauge under or beside anything. Overhanging branches, eaves and walls either block rain from reaching the gauge or funnel extra water into it, and either way the total is wrong. A rain gauge wants open sky above it and should sit clear of obstacles by at least twice their height, with its rim level and high enough to escape splashback from the ground.
The fifth is subtler: handling and not maintaining instruments. Touching the inside of a rain gauge leaves oils that change how water beads, letting a hygrometer get caked in dust slows its response, and never recalibrating anything means small drifts pile up over the years into a big error. A two-minute clean and an occasional accuracy check keep everything honest.
The thread running through all five is that good data is about discipline, not money. Put each instrument where it can measure what it is meant to measure, keep it clean, and check it now and then against a trustworthy live reference for your own location. Do that, and a modest home setup will quietly outperform an expensive one that nobody bothered to site properly.