If you’re a wikipedia wonk, the sort of person who reads not just the articles but the associated Talk pages where editors discuss the article, you might have seen the claim earlier this week on the Talk page for Mt. Washington that the peak broke its all-time high temperature during the early July heat wave:
Seems to be breaking records on the reg along w/ rest of the world. 73 degrees would be a new all time record high for Mount Washington
It included a link to a chart by Weather.com (here) that indeed showed 73 degrees on July 5, which would break the previous high (set several times) of 72.
I am a wikipedia wonk, so I noticed this – and was surprised I hadn’t heard about it. I checked with the Mt. Washington Observatory and they said, basically, BZZZZZZZT – wrong! The actual high that day was 71, as seen here. Following up, they said:
You’ll notice several values [on the Weather.com chart] do not match; so it is likely approximating our values based on algorithms of neighboring data for some reason.
The lesson learned here: Check your sources.