In any weather, you can have fun with your friend by doing activities like:

Going for a walk in the rain and jumping in puddlesHaving a picnic in the park on a sunny dayGoing sledding or building a snowman in the winterWatching a movie or playing board games indoors on a rainy dayGoing for a bike ride or hike on a nice day

What you might not do in certain weather conditions:

Avoiding outdoor activities during a thunderstorm or extreme heatStaying indoors during a snowstorm or heavy rainCanceling outdoor plans if there is a severe weather warningAvoiding water activities like swimming in cold, rainy weather

Overall, there are plenty of fun activities you can do with your friend in any weather, just remember to stay safe and comfortable based on the conditions.