Overview

As is evident from the map, the Havis area is a bay and peninsula, and seafaring is a common way to get around the area. Seafaring is also challenging due to the number of islands that obstruct the main routes for trade, so overland and river-based travel is actually more common.

Map

I wanted a cozier feel to this world, so the setting is focused on a smallish area that real humans can travel around in reasonably, not a whole continent. 1 hex is 20 km across in this map, and the whole map covers an area roughly 1200 by 560 km. More than standard “kingdom” scale. A normally moving party can cross 2 simple terrain hexes in a day (Per the PHB, pp181-182, 24mi - or 40km - per day, but most IRL long-trail thru-hikers average 15mi (24km) per day, so more like 1 hex per day). Some example distances:

• Bard's Gate to Lunaris is a 2 day journey. 
• Bard's Gate to Castorhage is 5 days. 
• Bard's Gate to Endhome is 12 days (by The Great Forest Road).

Click to embiggen. This map was made with the Wonderdraft, so it looks amazing and I fully recommend it.

Earth Comparison

Given the size of the space, one could think of it almost in terms of Anglo-Saxon Britain, that is, the various old kingdoms of Anglia, Essex, Kent, Mercia, Sussex, Wessex, Wales, Northumbria, etc. occupying about the same size area as this map covers. 

Settlements

I'm basically re-printing the same info from pp17-18 of the 5e DMG.  WOTC - feel free to tell me to take it down.

• Villages are not marked on the detailed map, but have a population less than 1000
• Towns have a population of 1000-6000
• Small Cities have a population of 6000-10000
• Large Cities and Capitals have a population of up to 25000, although Castorhage has almost 75000 poor souls.

Village

Population: Up to about 1,000
Government: A noble (usually not a resident) rules the village, with an appointed agent (a reeve) in residence to adjudicate disputes and collect taxes.
Defense: The reeve might have a small force of soldiers. Otherwise, the village relies on a citizen militia.
Commerce: Basic supplies are readily available, possibly from an inn or a trading post. Other goods are available from traveling merchants.
Organizations: A village might contain one or two temples or shrines, but few or no other organizations.

Most settlements are agricultural villages, supporting themselves and nearby towns or cities with crops and meat. Villagers produce food in one way or another - if not by tending the crops, then supporting those who do by shoeing horses, weaving clothes, milling grain, and the like. The goods they produce feed their families and supply trade with nearby settlements. A village's population is dispersed around a large area of land. Farmers live on their land, which spreads them widely around the village center. At the heart of the village, a handful of structures cluster together: a well, a marketplace, a small temple or two, a gathering place, and perhaps an inn for travelers.

Town

Population: Up to about 6,000
Government: A resident noble rules and appoints a lord mayor to oversee administration. An elected town council represents the interests of the middle class.
Defense: The noble commands a sizable army of professional soldiers, as well as personal bodyguards.
Commerce: Basic supplies are readily available, though exotic goods and services are harder to find. Inns and taverns support travelers.Organizations: The town contains several temples, as well as various merchant guilds and other organizations.

Towns are major trade centers, situated where important industries and reliable trade routes enabled the population to grow. These settlements rely on commerce. The import of raw materials and food from surrounding villages, and the export of crafted items to those villages, as well as to other towns and cities. A town's population is more diverse than that of most villages. Towns arise where roads intersect waterways, at the meeting of major land trade routes, around strategic defensive locations, or near significant mines or similar natural resources.

City

Population: Up to about 25,000
Government: A resident noble presides, with several other nobles sharing responsibility for surrounding areas and government functions. One such noble is the lord mayor, who oversees the city administration. An elected city council represents the middle class and might hold more actual power than the lord mayor. Other groups serve as important power centers as well.
Defense: The city supports an army of professional soldiers, guards, and town watch. Each noble in residence maintains a small force of personal bodyguards.
Commerce: Almost any goods or services are readily available. Many inns and taverns support travelers.
Organizations: A multitude of temples, guilds, and other organizations, some of which hold significant power in city affairs, can be found within the city's walls.

Cities are cradles of civilization. Their larger populations require considerable support from both surrounding villages and trade routes, so they're rare. Cities typically thrive in areas where large expanses of fertile, arable land surround a location accessible to trade, almost always on a navigable waterway. Cities almost always have walls, and the stages of a city's growth are easily identified by the expansion of the walls beyond the central core. These internal walls naturally divide the city into wards (neighborhoods defined by specific features), which have their own representatives on the city council and their own noble administrators. Cities that hold more than twenty-five thousand people are extremely rare. Metropolises such as Bard's Gate stand as vital beacons of civilization, or Castorhage as a den of depravity.

Seasons and Festivals

I’m a little torn about this. I think I’ll just use the Greyhawk norm. I don’t know if that’s infringement, but I DID buy a copy of the boxed set in the mid-1980s!  WOTC - tell me to stop if you want.

Week

Starday = Work

Sunday = Work

Moonday = Work

Feyday = Worship

Waterday = Work

Earthday = Work

Freeday = Rest

Year and festivals

360 days, 12 months of 30 days each, with 4 festivals

Needfest (New Year, winter solstice)

Fireseek = Winter

Readying = Spring

Coldeven = Spring

Growfest (Vernal equinox)

Planting = Low Summer

Flocktime = Low Summer

Wealsun = Low Summer

Richfest (Summer solstice)

Reaping = High Summer

Goodmonth = High Summer

Harvester = High Summer

Brewfest (autumnal equinox)

Patchwall = Autumn

Ready’reat = Autumn

Sunsebb = Winter

Climate

It is totally true that there’s no way that these climate variations could be this dramatic over 300km (which would only be slightly more than 2,5 degrees of latitude), especially with all that maritime moderation. But, this is still a D&D game, and I want a small scale, but different climate zones. So, I’ll do what I want. :-p

Southern Latitudes

The steppes around Silith are high scrub desert (not rolling dunes), but can still be very hot in the day and cold at night. Think the Sonora desert in Arizona. The southlands of the Swelter are also quite hot, but the thick humidity traps the heat and gives the area it’s name. Think the Everglades in Florida. Summer daytime highs can reach nearly 40C, and winter lows rarely dip below 10C in the Swelter, or 0C in the Galdus Steppes desert.

Northern Latitudes

The Frost Reaches, Far Borea, North Skywall Mountains, and Far Marches are more boreal climates, with cold, biting winters, and warm summers that, at least in Far Borea, are riddled with buzzing, biting insects. Think northern Minnesota (for the woods of Far Borea) or northern Montana (for the mountain areas). Summer daytime highs are usually around 18-24C, and winter lows frequently approach -18C. Not too much farther off the map to the north is ice sheets, and the mountains have numerous year-round glaciers.

Central Latitudes

Most of the region is temperate forests, grasslands, and scrubby hills. Think Central Europe. Summer time highs can be 30C and the Winter time lows average around -6C.