The rain forecast says 80%. That tells you surprisingly little about whether to go for a walk. A short shower near home, rain all afternoon on a moor, and heavy rain falling on an already swollen river need different decisions.
Read the forecast against the route. When will the rain arrive? Where will you be then? Add wind, temperature and visibility to the picture, particularly if there is a long exposed section. The Met Office mountain forecasts include these details for hill areas; their forecast guide explains how to read them. Look at the written forecast as well as the symbols.
Make the decision before the car park
Once everyone has travelled to the start, abandoning the plan feels harder. You have put on your boots and perhaps driven an hour. None of that changes the conditions on the hill.
Have a second route ready at home. For a wet day, look for straightforward navigation, a manageable distance and a safe way to shorten the walk. Check the awkward bits carefully: stepping stones, a riverside path liable to flood, or a long ridge where wind might affect balance.
Low ground needs checking too. Trees can be a problem in strong winds, and a surfaced path may be under water or closed. Read local access notices. If neither route looks sensible, leave the boots by the door.
The return leg deserves particular attention where water is involved. A crossing you manage in the morning may be a different prospect after hours of rain. The Met Office's mountain-safety advice explains how persistent rain, cold and wind can combine, and how conditions at water crossings can change.
Keeping a dry layer for later
Put on the waterproof before steady rain has soaked your other clothes. Keep it near the top of the bag, adjust the hood and close the cuffs. There is little point carrying it for the first wet hour.
Protect a spare warm layer inside the rucksack. You may feel warm while moving and then cool quickly at a stop. Think about lunch beforehand: food you can eat during a brief sheltered pause may be more useful than a meal needing a long sit-down. Carry it even if there is a café on the route.
Wet-weather kit needs to work while you are using it. Can you read the map, reach a snack and take a drink without unpacking the bag in the rain? Check at home if the arrangement is unfamiliar.
Watch what is happening, rather than waiting for the forecast to be right
The forecast is part of the plan. On the walk, pay attention to what you can actually see and how people are coping.
Someone who is getting cold despite the clothing available needs a change of plan. So do wind affecting balance, a doubtful crossing or visibility in which you cannot navigate confidently. If progress has slowed enough to threaten your daylight margin, use a safe shorter route while there is still time.
Agree these decisions with the group early. It helps to name the junction where you could take a shorter permitted loop, rather than relying on a vague promise to turn back if necessary. Avoid committing to a crossing you may be unable to use on the return.
Afterwards, put useful detail in any Walkmates route notes. Give the location, date and conditions: deep mud on a particular field section after several wet days, for example. Report an urgent hazard or access problem to the authority or land manager as well. They may never see a comment on the route.
Unpack when you get home. The damp gloves in a side pocket are easy to overlook until the next walk.
For kit, see what to pack for a day walk. If the route crosses livestock fields, read cattle, dogs and gates.