Most likely there was lightning and thunder, a terrible storm which caused the Philistines to panic1 and enabled the Israelites to defeat them in battle (even though they were not prepared).2 The storm would have been similar to the one that had previously routed the Amorites (Joshua 10:11–12) and bogged down the chariots of Sisera (Judges 5:20–21).3 This was a very literal fulfillment of Hannah's prayer in 1 Samuel 2:10.4 The Lord’s self-revelation in the storm is particularly significant seeing as the Israelites had just thrown away their Baal statues. Then the Lord revealed himself in a Baal-like manner to prove that he, and not the Canaanite storm god Baal, controls nature and possesses the capacity to bless Israel with fertility.5
10 As Samuel was offering up the burnt offering, the Philistines drew near to attack Israel. But the LORD thundered with a mighty sound that day against the Philistines and threw them into confusion, and they were defeated before Israel.