It's October. Up and down the country, thousands of cyclists are being struck with nausea, dizziness, shortness of breath, burning limbs and blurred vision. This is not some weirdly selective early winter virus – all these symptoms are self-inflicted. October is the month for hill climbs and suffering is what hill climbs are all about.

Cycling clubs in the UK traditionally end the racing season by holding hill climbs. A vertical time trial, these races involve groups of riders gathering at the bottom of a hill and then, at one minute intervals, riding up it as fast as they can to see who can set the quickest time. Some of the hills are legendary, with names like Monsal Head or the Rake, names that bring most cyclists out in a cold sweat. It's the absence of the long mountain passes prevalent in the Alps that has given British hill climbs their unique flavour. Short and brutal, they test riders like no other race.

"A good hill climb has to be no longer than two miles, and steep, very steep" says Simon Warren, author of 100 Greatest Cycling Climbs.

"It needs a corner, maybe some geographical drama for a backdrop and most importantly, it must attract a large crowd of spectators, there's no joy in suffering in silence."

Those crowds generally flock to the better known hills for "open" events. These races attract large fields of up to 150 riders to compete for cash prizes. For amateur riders, the special atmosphere of these events is perhaps their only chance to get a feel of what the professionals experience on the famous climbs of the Tour de France. Spectators line the road, sometimes up to three deep, screaming encouragement to all competitors.

The Cycling Time Trials website lists 70 open events in 2011, 49 of them in October. The National Hill Climb at the end of the month is the biggest draw, featuring the cream of British climbing talent. One of the favourites for this year's race is Tejvan Pettinger. For him, the appeal of the hill climb is simple:

"I love cycling up hills. It's a challenge to see how much you can push yourself out of your comfort zone."

Tall and lean, Tejvan is not the stereotypical British hill climber – the short, sharp hills generally suit a small, strong rider with explosive power. Luckily for him, this year's nationals take place on the aptly named Long Hill, just outside Buxton – a hill he holds the course record for, proof that it's more than just build that influences a rider's prowess. Warren explains:

"Some riders are born to race hill climbs. They possess the natural athletic ability coupled with the extraordinary pain threshold that allows them to compete in this specialist discipline."

While only a handful have the ability to win the bigger races, the success of these events depends on those mere mortals that make up the numbers. Indeed thousands of riders, with absolutely no prospect of winning, take part in the hundreds of club hill climbs that don't make it onto the time trials event list. Warren says:

"I think hill climbs owe their success to their quirkiness, they have long been a forgotten discipline and that is now their attraction. The madness of pushing yourself to the point of collapse up a stupidly steep hill, of riding so hard you see stars, doing it for enjoyment and even sicker, for entertainment, is having real resonance at the moment."

It's an attraction that inspired Paul Churchill of cycle sport Rollapaluza to set up the Urban Hill Climb on Swains Lane in Highgate, London.

"It has turned out to be hugely popular among riders of all abilities. Places on this year's race sold out within three minutes of the launch."

"The format of our Urban Hill Climb is great for spectators too as they get to see the competitors close up and not just whizzing past as they might at a road race."

The Urban Hill Climb is only in its second year, but there are more venerable events out there. The Catford CC climb in Kent is the oldest continuing bike race in the world. The first time it ran, in 1887, the fourth placed finisher was riding a Penny Farthing. Renowned for its enthusiastic crowds, it still attracts the top riders to sample its extraordinary atmosphere and try to conquer its 25% gradients. Why does this all take place in October? Generally cold and wet, it is not a month renowned for its good weather. Warren says:

"Because that's the way it's always been. Hill climbs are the cherry on the cake of the season, one last blast before winter sets in. Despite their growing popularity it's still only the few who are mad enough to take part so that leaves plenty of other cyclists who've already finished racing to come and watch. They therefore become great social events and the air is filled with celebration and relief as one by one the riders squeeze out one last effort before they settle down to enjoy a few months of cake and beer."



• Andy Ward loves hill climbs and is a contributor to the Daily Cycle Hill Climber's Guide