Weatherlight is a small set with 62 commons, 55 uncommons, and 50 rares. This is the same size as the previous small set, Visions. The set was printed in English in Belgium. The existence of US-printed English Weatherlight is unknown. 
Weatherlight was sold in 15 card booster packs. Booster boxes have 36 packs.
The Belgian printing uses striped collation with 10 × 11 sheets and (probably) 10 × 10 sheets. Packs are back-facing and contain 3 uncommons, 1 rare, and 11 commons (in that order).
|3 Uncommons||1 Rare||11 Commons|
There are two groups of commons. Most commons are in group B which consists of 55 commons, each printed twice on a 10 × 11 sheet. The remaining 7 commons are in group A. The first common in every pack is from group A, and the rest are from group B.
This common configuration is the same as the Belgian printing of Visions. (No packs have been observed with more than one A common.) Consequently, it is likely that group A is printed on the top half of a 10 × 10 rare sheet with 6 cards showing up 7 times and one card showing up 8 times. Without a picture of the sheet, it will be difficult to figure out which card shows up more often. The cards that show up 7 times will be 77/100 as common as B commons, and the one that shows up 8 times will be 88/100 as common.
The cards in Group A are Shattered Crypt, Bogardan Firefiend, Tolarian Drake, Benalish Knight, Harvest Wurm, Jangling Automaton, and Mind Stone.
Group B consists of 55 cards each appearing twice on a sheet. The top row is chosen so that the colors match the corresponding Visions sheet (which has a picture), except for the bottom row which breaks the pattern anyway.
 The "Compilation of Manufacture Information for MTG Products" thread on the Magic Librarities Forum lists US-printed Weatherlight as uncertain. I also did not find any during my research.