Can you escape from the Web or Moonbeam spells using readied movement?

Question

Inspired by this question, I was wondering whether this works:

Web states:

Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw.

Whereas moonbeam states:

When a creature enters the spell's area for the first time on a turn or starts its turn there, it is engulfed in ghostly flames that cause searing pain, and it must make a Constitution saving throw.

And the description of the Ready action states the following (from PHB page 193; emphasis mine):

First, you decide what perceivable circumstance will trigger your reaction. Then, you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it.

Assuming whatever trigger your readied action had does actually occur before the start of your next turn, can you escape from these spells?

It is possible for this to occur through chance. Say you had already readied movement, and then it happened that a creature cast moonbeam on you, and then your trigger (unrelated to moonbeam) occurred. Alternatively, if a creature readied (and thus cast) moonbeam and somebody identified the spell, you could ready movement as a cautionary measure to avoid taking the damage if the creature placed the moonbeam over you.

This is also similar to scenarios where an ally could allow you to move, such as the Battle Master Fighter's Maneuvering Attack Maneuver, or if an ally directly moved you, such as through grappling.

Answer 1

You can at least escape from web and almost certainly moonbeam as well

Web is a more straightforward case; as stated in the question, it says (emphasis mine):

Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw.

And if you already took the Ready action to move on your previous turn (with a trigger that occurs), then you are able to move away from the webs before your turn has occurred and so you do not make the saving throw.

Note, this logic does mean that you can go through the webbing (not just from the inside to the outside) by using readied movement, as you would not be entering the webs on your own turn.

Moonbeam is slightly more complicated, as it has the following wording (emphasis mine):

When a creature enters the spell's area for the first time on a turn or starts its turn there, it is engulfed in ghostly flames that cause searing pain, and it must make a Constitution saving throw.

This brings up the question of whether or not the creature has entered the spell's area. Luckily this has been elaborated on in the Sage Advice Compendium as follows (bolded statement mine):

Our design intent for such spells [as moonbeam] is this: a creature enters the area of effect when the creature passes into it. Creating the area of effect on the creature or moving it onto the creature doesn’t count. If the creature is still in the area at the start of its turn, it is subjected to the area’s effect.

Thus the creating of the moonbeam area of effect does not trigger a save, and the creature does not have to make one at the time of the casting.

There is the issue of when exactly has a creature "passed into" an area of effect. But to me this requires actually going into, actually entering, an area of effect. Thus using readied movement to go from being inside the area of effect to being outside of it would not trigger any save because you have not passed into the area, you've simply moved through it.

This definition of "enter" is further supported by this Q/A which rules that you do not repeat the saving throw for webs simply because you walk through them, but instead you have to actually go into the area of effect.