Per the wilderness turn of the hazard system, locality events are mechanical changes in the area you're in. What does this mean for pointcrawling a city?
There are two things to consider - the scope of the locality event, as well as what it is. The scope could be the node the PCs are currently in. Perhaps a smallish riot breaks out, or a street play, which guards will try to shut down for blocking roads. Perhaps a literal fire sale at a store, a palatial parade. Some of these wouldn't necessarily affect an entire neighborhood. Some would route around through different nodes with (tiny) minds of their own.
This is also an opportunity to bring in Haven events as described in the system. So perhaps a bomb goes off and guard patrols become more common (and less likely to shake people down, as their coworkers are everywhere). Haven events will definitely affect every single node the PCs can go to in the urban pointcrawl. They could spur adventures and change the entire reason the PCs are in the city in the first place. The PCs might seek to flee the city only to find, in Charmonde's case, that its screaming walls are up and walking away would lead to death. Or in other towns, getting out has become onerous (not impossible) as the culprits could get away, or enemies are outside the walls, or the priests said the devil is bathing in the moat. It's not impossible to leave - it's just not easy. And finding a route out would be valuable information for many people in the city.
Haven events in a given urbancrawl turn should still be haven events. They should affect the city for weeks or months, and to make sure the entire world doesn't seem to be ending, they typically shouldn't pile up on top of one another every 20 minutes, or hour, or however often you roll for a turn passing. Winter and a jailbreak and an insurrection and a monster invasion is just too much for the tone of my game, but feel free to pile them up if fitting your own style. Personally, if I roll a locality event, and a haven event from that, haven events are off the table for the rest of my two-hour session. Probably for longer.
For Charmonde, my locality event table will look like this. Roll a d6 and
- Bridge Slavers Student Festival - likely university students performing theatre, getting guards off the PC's backs, and occasionally making good anti-slavery points. Or just being drunks.
- Crater Day - citizens celebrate the last defensive war Charmonde had. The reasons for the war and the source of the crater are contradictory. Food and drink are cheap, crowds are rife with thieves.
- Nobles Duel at Pauper's Bridge - it seems like everyone wants to turn out and hang off the narrow bridge, watching the offended party and the offendor duel with smallswords atop the bridge's highest tier. Gambling and an unofficial pre-duel show of acrobatics and fighting prowess.
- Royal parade winds through much of the city and every bridge. Dress codes will be strictly enforced, and waves of guards will pass through before the Queen to check for illicit speech or roguish characters.
- The sonic wall misfires and no one can get into or out of the city for half a day. Anything that can sell out in that time period is going to sell out, and people will bemoan the lack of control their betters have. Quietly, of course. Rabble-rousing is a crime.
- Roll on the Haven Events table. If re-rolled, the PCs feel as though someone stepped over their graves.