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Campaign Weather Generator

Thirty days of weather with a real year behind it — long irregular summers and winters, the occasional brutal one, and per-day effects on marching, foraging and how far your scouts can see.

Weather at a table is only worth tracking if it has memory. A generator that rolls each day independently gives you a blizzard on Tuesday and a heatwave on Wednesday, and after two sessions everyone quietly stops asking what the sky is doing.

This one has seasons underneath it — long, irregular ones — so the thirty days you get are a stretch of a year rather than thirty unrelated rolls. Winter arrives, stays for weeks, and costs you something the whole time.

Where the weather comes from

Not from a d20 table. The season calendars here are generated by the season engine of the strategy game this site belongs to, and the numbers in the March, Forage and Sight columns are that game's real modifiers, read out of its code when this page was built.

That model does three things a hand-written table does not:

• Seasons run long and unequal. A summer might hold for fifty days or a hundred and ten; a winter for forty or ninety. Autumn and spring are short transitions. You cannot predict the length from the season, which is the entire reason “winter is coming” is a threat rather than a date.
• One winter in six is worse. The engine occasionally rolls a Long Night — a winter roughly twice the usual length with every penalty deepened. If one lands inside your thirty days you will know, because the whole table changes colour.
• Every day carries consequences, not adjectives. Marching, foraging and visibility all move with the season, so “it is winter” becomes a set of rulings you can make instantly and consistently.

What each season actually does

These are the game's own figures. A multiplier of 0.75× on marching means a day's travel covers three quarters of the distance; 0.6× on foraging means a party living off the land finds well under two thirds of what it would in the same place in autumn.

The defender's bonus is the row that surprises people. In this model winter helps whoever is already inside the walls — the roads are bad, the besiegers are cold, and the granary was filled in autumn. If your campaign has a siege in it, checking the season before you set the date is the single highest-value use of this page.

The sky, and the one rule it obeys

The season decides what is plausible; the day decides what actually happens. Each day's sky is rolled from a weighting appropriate to its season and then passed through the game's own reconciliation rule, which enforces the obvious: rain falls as snow in winter, and a snow report in high summer reads as a heavy grey storm instead. That rule is not reimplemented here — its complete answer table was produced by calling the game's function once for every possible combination when this page was built, so it cannot disagree with the game.

The weighting itself is this page's, and it has to be: in the live game the sky comes from a real weather report for the world's anchor location, and a static page with no network connection has nothing to ask. So the dice are ours and the rules are the game's.

Using it at a table

Three habits make weather worth the effort and none of them take long:

• Announce it once, at dawn, in one sentence. Weather narrated every hour becomes wallpaper. Weather stated once a day, and then referred back to when it costs something, stays a fact.
• Let it be the reason. When a march takes longer than the party wanted, point at the March column rather than at a ruling. Players argue with a GM and accept a table.
• Foreshadow the turn. The almanac shows you the season boundaries in advance, which means you can have the locals start talking about the coming winter two sessions before it lands. Weather that was predicted is weather the table believes.

The download button hands you the whole thirty days as a plain table you can paste into notes or a spreadsheet, and the “next thirty days” button walks the same year forward so a long campaign keeps one continuous calendar rather than restarting the weather every month. The link at the top is permanent: the year, the starting day and the sky rolls are all packed into the address, so a co-GM opening it sees the same almanac you are looking at.

Why the winters are irregular

Because a predictable winter is a scheduling problem rather than a threat. If your players know the season turns on the sixtieth day of every year they will simply plan around it, and the whole mechanic becomes a calendar entry. Lengths drawn from a range mean the only honest answer to “how long until spring?” is “nobody knows, and the old people disagree” — which is both more interesting and, as it happens, closer to how pre-modern people actually talked about weather.

It also means a rolled year has a shape. Some are gentle: a long summer, a short winter, and a party that never has to think about food. Some are brutal, and those are the years a campaign remembers.

Can I use this almanac?

Yes — for anything, including commercial work, with no permission and no credit required. Short strings like a name or a two-word motto are not the kind of thing anyone can own, and the crest you compose is your composition, not ours. Take it to a novel, a tabletop campaign, a stream overlay, a band, a boat, a business card.

We ask for exactly nothing in return: no account, no email, no sign-up, no watermark. Nothing you type or click here is sent anywhere — every one of these tools runs entirely inside your own browser, so there is no server that could keep your design even if it wanted to. If you want to tell somebody where it came from, a link back is kind, but it is not a condition.

The rest of the table kit

tavern & inn · npc · quest hook · settlement · character backstory — all free, all instant, all of them working with the network switched off. The tabletop index lists the lot, and the wider tools workshop adds a coat of arms forge and five name generators for houses, castles, lords, mottoes and dragons.