I have been logging this on a raw EURUSD account at the offsets suggested above. Across most US releases the spread drifts from 0.1 to about 0.6 pips in the 15 seconds before, spikes to around 3 pips in the first two seconds, and is under 0.5 by roughly 30 seconds.

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The illustration above is a cleaned up composite of that shape with GBPJPY under EURUSD, not one specific release. The cross peaks near 9 pips and takes about four minutes to settle, so I leave crosses alone for the first five.
One consequence people miss is where stops trigger. A short position's stop sits on the ask, so a 3 pip spike can close a short at a level the bid line never printed.
The tick stream also thins out during the spike. My logger sometimes gets one quote every 300 to 500 ms there, so the recorded peak is probably lower than the real one.
The number I actually use is time back to under twice normal, which on EURUSD has been 30 to 60 seconds. I plan any entry after a release around that window, not the peak.
Do your logs show the widening starting earlier on NFP mornings? Mine do, by about ten seconds.