Are weak acids on the pH scale less than 3?

NO!!!!

The pH scale is from 0 to 14.

The lower the numerical value of the pH , then the stronger the acid.

e.g. pH = 1 Strongly acidic ( e.g. Hydrochloric Acid).

pH = 4 Weakly acidic ( e.g. Ethanoic (Acetic) acid).

pH = 7 Neutrality (Water)

pH = 9 Weakly Alkaline ( Ammonia Solution).

pH = 12 Strongly Alkaline ( Sodium Hydroxide).

pH = 14 Very strongly alkaline ( very weakly acidic ; in extremis).

NB The pH is the 'negative logarithm , to the base 10, of the hydrogen ion conc'n. Algebraically ; pH = -(log(10)[H^(+)])

The inverse maths. function is [H^(+)] = 10^(-pH).

So if you have a pH = 1

Then H^(+) = 10^(-1) = 0.1 ( Casually a tenth of the sol'n is hydrogen ions).

If you have a pH = 12

Then H^(+) = 10^(-12) = 0.000000000001 (Casually a trillionth of the solution is hydrogen ions; usually considered as strongly alkaline with a pOH = 0.01, an hundredth of the solution is hydroxide ions, compared to a trillionth( an extremely tiny amount), of hydrogen ions.