These figures are stated in:
Joshua BARNES. 1688. The History of that Most Victorious Monarch Edward III, King of England and France, and Lord of Ireland and First Founder of the Most Noble Order of the Garter: Being a Full and Exact Account of the Life and Death of the said King, Together with That of his Most renowned Son Edward, Prince of Wales and of Aquitain, sirnamed the Black Prince, Faithfully and carefully Collected from the Best and most Antient Authors Domestick and Foreign, Printed Books, Manuscripts and Records.
The pertinent passage is in Chapter VI of Book III (p. 583), and reads as follows:
But sure∣ly the Occasion which wholly brought him over was very remarkable, if not miracu∣lous; for presently upon these Words, while yet the King was inexorable, and refus'd to give the French Commissioners any agreeable Answer, there fell from Heaven such a wonderfull Storm and Tempest of Thunder, Lightning, Rain and Hail among the English Army, that it seem'd as if the whole Fabrick of Nature was falling to pieces; and withall it was so excessive Cold at the same time, that it cannot be imagin'd; so that together with all these Arrows of Gods Anger, there perished no less than 6000 Horses, and well-nigh a 1000 Men, among whom were several Persons of Quality. ... The boldest Heart of all these Valiant Souldiers trembled at the apprehension of this Dreadfull Judgment: But King Edward like a Good and Pious Prince, look'd upon it as a loud Declaration of the Divine Plea∣sure: Wherefore immediately alighting from his Horse, he kneeled down on the ground, and casting his Eyes toward the Church of our Lady of Chartres, made a solemn Vow to Almighty God, That he would now sincerely and absolutely incline his Mind to a final Peace with France, if he might obtain good Conditions; at which time also he made a Devout Confession of his sins, and so took up his Lodging in a Village near Chartres called Bretigny, where the French Commissioners being come the next day with more ample Instructions, the King was content to accept of Peace.
A number of sources for this story are quoted on that page, especially Froissart. The text of the citation is
Frois. c. 211. f. 105. Du Ches. p. 684. Mezeray p. 59. Walsing. hist. p. 167. n. 30 Knighton p. 2624. n. 10. M.S. vet. Angl. in Bibl. C.C.C. Cantab. c. 230. Ashmole p. 660. Jacob. Meyer Annal. Flandr. l. 13 p. 184. & Odor. Rainal. & omnes.