1) Here's a link to NOAA's,National Weather Service, 48-hour continuous weather data-logging.
2) If you live near a major airport, the NOAA', 48-hour weather summary for that airport, can provide the barometric data, on a 24-hour basis, to augment local airport automated weather observation service (AWOS ) data, like temperature, dew point, relative humidity, wind speed, wind direction, altimeter setting ( barometric pressure ),etc..
3) If you can conduct your testing within a one-hour window time-frame, this data summary material can assist you in reducing your test data to SAE Standard conditions, based upon actual air density, winds, and wind spectra, etc..
4) Caution needs to be taken with respect to the 'altimeter' data, as it's been modified to quickly inform pilots as to whether they're flying into a 'low', 'steady', or 'high' pressure area, all of which control the flight weather they'll encounter en route.
5) There are online tools which can help you convert the 'altimeter' reading to 'raw' barometric pressure, necessary for local stagnation-static, and dynamic pressures experienced and recorded while conducting your road tests.
6) Laboratory-grade meteorological instruments are expensive and must be routinely calibrated.
7) Might as well use NOAA's. You've paid for them.
8) The Dallas Fort Worth International Airport data is just an example of what's offered.
9) As the late Robert Parsons would say, 'It's way out ahead of nothin'.
https://w1.weather.gov/obhistory/KDFW.html