What I’ve noticed about ASOS is aside from hourly and special observations (which are reported as the actual temperature in deg F or rounded to the nearest deg F), the 5 min observations are rounded to the nearest deg C and converted to deg F. This brings in rounding error on the Fahrenheit scale. For example, if ASOS is actually reading 10.5C, it converts to 50.9F. The problem is the 5 min ASOS report will round 10.5C to 11C and that converts to 51.8F. So it can make temperature look artificially high or low depending on the rounding, but never more than 1degF. What I’ve also noticed is despite this, ASOS will report the correct max of 51F not the incorrect 52F even when the 5 min obs was reported as 52! If you convert the 5 min ASOS obs from F to C, you’ll notice it always converts to the whole deg C. So you have to be careful with the temp comparisons using 5 min obs from ASOS.
In the example above, 48.2F is 9C. 50.0F is 10C. The actual temp was probably bouncing between 9.4C and 9.5C, but it shows up as a 2degF swing. The hourly obs at 6:52 of 48.9F is the actual temp in degF which converts to 9.4C and that is what is reported as the min instead of the rounded (and erroneous) 48.2F.