I rode a short loop outside of town four times back to back today so virtually the same conditions, same bike, etc. I have one segment on that loop which today was into the wind riding on a snow covered shoulder. I averaged 10.1, 10.5, 10.9 and 10.2 mph on that segment during the four times around the loop. Strava said my average power on that segment varied from 58 to 109 watts, but get this, my slowest time (10.1 mph) showed the highest wattage. Looking at the analysis I averaged 81 watts (which I can believe as this was a slow, recreational winter ride) but my peak was over 1,000 watts, three different times at three different points in the loop Strava also said that I had a max speed of 19 mph which I also know to be inaccurate as with the snowy road surface and my on bike computer I know that I didn't pass 15 mph even with the wind at my back.
I've noticed this before on other rides, but this is the first time I had four virtually identical passes on the exact same segment in such short order. I don't expect 100% accuracy but this makes me question any or all of the wattage estimates that I have gotten from Strava.