The Intricacies of Thunder and Luck in Stardew Valley

Stardew Valley, a charming life simulation game, provides an intricate world for players to explore. One fascinating aspect of this pixel-art farming utopia is its weather system, specifically thunderstorms. In this article, we’ll delve deep into how your daily luck and luck-enhancing items affect thunderstorms and what gets struck during these events.

The Thunder Probability Formula

Before diving into the nitty-gritty details, let’s first look at the basic formula governing thunder probability in the game:

Thunder Probability = 0.125 + Daily Luck + (Luck Boost/100)

  • Base Thunder Probability: 12.5%
  • Daily Luck: Your daily luck as specified by the TV’s Fortune Teller or other sources.
  • Luck Boost: Additional luck gained from items such as Lucky Rings.

Thunder is evaluated every 10 minutes in-game, from 6 a.m. to 12 a.m., resulting in a total of 107 checks per day.

What Does this Mean for Average Thunder?

If you have zero daily luck and no luck boost, you would have a 12.5% chance of thunder occurring at each check. Over the course of 107 checks, this translates to an average of approximately 13.375 thunder strikes per day.

This probability functions as a pseudo-random variable; it doesn’t vary much if your luck remains the same throughout the day.

The Time Factor

The time you choose to sleep also plays a role. If you go to bed before midnight, the game will still evaluate the probability for the remaining time slots until either a thunder strike is determined or the clock hits midnight.

For instance, if you have thunder predicted at 10 a.m. and 3 p.m.:

  • Sleep before 10 a.m.: Only 1 thunder.
  • Sleep between 10 a.m. and 3 p.m.: 2 thunders.
  • Sleep after 3 p.m.: Still 2 thunders.
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Note that you cannot artificially increase the number of thunders by sleeping early if no more are programmed for that day.

Maximum Thunder in a Day

The maximum daily luck you can have is 0.125, and the highest luck boost is 9. If you sum these up, the thunder probability peaks at 34%. When this is applied across 107 checks, it results in approximately 36.38 thunder occurrences. Given some randomness, you can potentially have over 40 thunders in a single day.


Battery Packs vs. Thunder

It’s crucial to note that the number of thunders doesn’t equal the number of Battery Packs you’ll get. The number of Battery Packs you’ll receive depends on the number of Lightning Rods you have on your farm.

Influence of Luck on Thunder

Even at the worst luck, you would still get around 2.675 thunders. Because there is some variability, it’s also possible to get just one thunder on some days.

Adding luck-boosting items can make a modest difference:

  • One Lucky Ring adds roughly 1% chance, equating to about 1.07 extra thunders.
  • Two Lucky Rings would result in 2.14 extra thunders.
  • Consuming a Lucky Ice Cream can result in about 5.35 extra thunders.

Impact on Crops and Farm Items

Another formula determines the chance of thunder striking your crops or other items:

Strike Probability = 0.25 – Daily Luck – (Luck Boost/100)

The higher your luck, the less likely your crops will be struck by thunder. The highest and lowest probabilities for an item to be struck are 35% and 3.5%, respectively. The average number of times an item will be struck varies minimally between the highest and lowest luck scenarios.

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What Gets Struck

Thunder will not target Scarecrows, Kegs, or similar items. It focuses on Trees, Flooring, and Crops. If you have many trees and flooring on your farm, they can help distribute the chances and save your crops from being struck.

trees, flooring, and crops that can be affected by thunder strikes
trees, flooring, and crops that can be affected by thunder strikes


Thunderstorms in Stardew Valley are more than just a visual spectacle; they involve complex interactions with your daily luck and luck-boosting items. Whether you are looking to maximize Battery Packs or save your precious crops, understanding these intricacies can give you an edge.

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