I have added a bit of extra contextual information in the sidebar next to every diary entry. You can now see:
The average temperature for that month (daily data isn’t available until 1772) as recorded by Gordon Manley of the Royal Meteorological Society. You can view the full dataset on the Met Office’s website.
My thanks to Terry Foreman for finding both these sources of information that help bring Pepys’ world alive. If anyone can suggest anything else, do let me know.