Today it rained.

today:
<h, e, x1>
{ MOD:<h, x1, _> }
{ h:on(e, x1, x2) h:this-day(x2) }

rain lexical entry
< h3, e4, _ >
{}
{ h3:rain(e4) }
{}
{}

adjunct extraction LR: 

< h3, e4, _ >
{ GAPS:[ <h3, e4, _> ], MOD:<h3, e4, _> }
{}
{}
{}