I ran over to him, thinking he'd severed a limb, to find him sobbing by the side of his bike.
"Are you OK, son? Where does it hurt?" I asked him.
But all he could force from his lips was a stuttered "M-m-my h-h-hat's bl-bl-blown a-a-away" with a plaintive finger pointing at some bushes where it had escaped to.
"Crikey, lad," I said, both relieved and irritated. 'I thought something serious had happened.'
But this is the nature of my son. He cries at everything. He cries if he loses a race, even if it's against bigger, stronger, older boys. He cries if he can't get his pyjamas on before his little brother. He cries if he can't read a word, even if that word is something that should be well beyond his reach ("diarrhoea" was the most recent one). He cries if I ask him to get in the bath, especially if it interrupts a game he's just about to finish. He cries if I ask him to get out of the bath. He cries if I've run out of his favourite Cheerios for breakfast.
And when he's not crying, he clams up and goes into a monstrous sulk.
The other day, he asked if he could have a friend round for a play date. I hesitated for a micro-second, and his bottom lip came out like a canopy over a shop front.
"It doesn't matter," he said. Then skulked off to his room.
All of this, I've concluded, is evidence that my son is a sufferer of Hypersensitive Boy Syndrome. It's not a medical term, but it is a condition many parents will be familiar with.
Do a quick Google search and you will find banks and banks of forums populated by frustrated parents, many of them agitated and bemused by the fact their offspring dissolves into tears at the slightest provocation.
The U.S. website, Terrific Parenting devoted a whole section to the subject.
"Young children often are easily upset by minor circumstances," it says. "Perhaps they break a toy, or can't watch their favorite program, or have to leave the playground before they're ready. These and other everyday situations can give rise to sadness, whining, and crying.
"Of course, some circumstances warrant an emotional response, for example, if another child takes their toy or a peer treats them unfairly or harshly. Children may react emotionally in many situations; what's important is whether the intensity of the response is appropriate.
"As overly sensitive children get older, parents often see more extreme, melodramatic outbursts that continue for an extended time. In school, such outbursts elicit negative attention and impede their ability to get along.
"Extreme reactions to relatively minor events often lead to interventions by parents and teachers. It may seem necessary to respond to these outbursts to help the child calm down. However, as the child gets older, the outbursts seem to increase rather than decrease, and parents spend more and more time trying to calm the child. This solution is actually the problem."
I don't think my own son is quite as bad as that, but some children are so hypersensitive that they drive their parents to their wits' end.
One mother wrote on the parenting site Café Mom: "We should start a support group for moms with crybaby kids!! Some days I want to throw my daughter out of the window. She cries all the time. I don't even know why she cries most of the time. Sometimes, she doesn't even know why she's crying. We have told her that while it's OK to feel and show emotions, there is no way that she should be crying so much. We have explained to her that when she cries so much, it doesn't mean as much to us as it would if she only cried, say, oh, once a day or so. Then when she really should be crying, we don't even want to hear it because it's all we've been hearing."
Another wrote of her five year-old on Mothering: "If we go to a restaurant and they don't have what he wants to drink he'll cry, if he changes his mind after he's ordered his food he'll cry, if he asks for candy and we say no he'll cry. Anything will set it off."
I hear you, mums!
The upside of having a hypersensitive child is the incredible amount of love and affection you receive from them. My son still kisses me when I drop him off at school, and the way he cuddles his four year-old brother, just for the sake of it, brings out the cry-baby in me, too. He is also extremely tuned in to the emotions of others: he knows when someone is upset and is the first to offer empathy.
But what worries me is the future. I went to a tough comprehensive school in Manchester, and if you burst into tears there over little or nothing, you'd end up on the receiving end of a good hiding, or worse, become the victim of bullying.
The boys at my own son's primary school are polite and kind, but a few of them are more rugged than he is, and as they grow up, develop muscles and a penchant for sport, I'm concerned my child will end up being left behind. I've tried to explain this to my lad, but his mother wisely counsels that I'm being, well, hypersensitive myself.
Why are some children more sensitive than others? According to Dr Elaine Aron, author of The Highly Sensitive Person, it's just something they're born with, and not a product of socialisation or a lack of confidence. And it's not something we parents can control.
Sensitive children have more exaggerated reactions to things, which is sadly often seen as a weakness. But the opposite is true, according to family therapist Jeremy G. Schneider.
"The reality is that sensitive children have a gift," he said. "They are able to experience the world at a higher level than average children.'
I've read that last sentence several times and, do you know what? I like it. I like it a lot.
Because it means my sensitive little boy isn't a cry-baby softie: he's a gifted child who's way above average.