Both the USA and Canada are huge countries. The climate varies considerably between different regions.

The whole of the USA and most of the densely inhabited areas of Canada are at a much more southerly latitude than Britain. For example, New York City is at approximately the same latitude as Rome (Italy) and Los Angeles roughly the same as Casablanca (Morocco). Even Winnipeg, thought of as being well north, is at approximately the same latitude as Brussels (Belgium).

The other vital factors which influence the climate are oceans and mountain ranges. In the northern hemisphere clouds that build up over the oceans move eastwards. In North America these clouds deposit most of their rain on the coastal mountains and the Sierra Nevada and Cascade mountain ranges (which is why the giant redwood and sequoia trees grow there). This means that the regions to the east of these mountain ranges rarely receive much rainfall or much cloud cover. The same effect applies to regions east of the Rocky Mountains. The frequent lack of cloud cover means that large areas of the interior of the North American continent tend to experience very hot summers and very cold winters.

The more southerly latitude has another important effect - the length of daylight. Being nearer the equator, the effects of the seasonal changes are far less than nearer the poles where they are at their most extreme. This means that in summer the southern part of the USA has noticeably less hours of daylight than Britain, while in winter it has more.

The whole of the south of the USA is normally extremely hot from May to September, with the southwest usually being very hot and dry, and the southeast usually being almost unbearably hot and humid. As you head further to the north the temperatures tend to be slightly cooler and the risk of cloud increases. Large parts of the USA tend to suffer from violent but brief thunderstorms most afternoons during the summer.

Some of the high passes over the Rockies and the Sierras don't open until the snow melts in June, and they may be temporarily closed by late snow falls even then. The high passes tend to close when the first heavy snow falls occur fairly early in the autumn. For example, the Tioga Pass over the Sierra Nevada Mountains through Yosemite National Park in California is normally closed from October to May, while the Going-to-the-Sun road over Logan Pass in Glacier National Park in Montana doesn't usually open until early June. Roads over the Smoky Mountains in the southern part of Appalachia (North Carolina and Tennessee) can be affected by snow even as late as April.

While planning when to visit the USA or Canada you also need to consider how the air fares change, often quite drastically, depending on the time of year, and how the cost and availability of accommodation are affected by the American summer holiday season. By joining a group tour you eliminate most of those worries, off course. For any holiday that includes the Rockies, June is the ideal time. For Florida, early spring or late autumn would probably be best.

Because of the reflected glare from the road surface, sun glasses are recommended when driving. Because of the heat, a folding cardboard sunshade which can be put up on the inside of the windscreen when the car is parked is recommended. These are widely available very cheaply, and will help keep the temperature of the steering wheel down to a level where it is possible to touch it after the car has been parked for a while. Because of the heat from the sun, a wide brimmed hat is an excellent idea when walking. All rental cars and most buildings (including motels, shops and restaurants) have air conditioning. Remember that for air conditioning to have any effect all windows must be closed.

Some brief climate information can be found on the "Introduction" page for each American State and Canadian Province and Territory in the State and Province Index.

Finally, no discussion of the climate of the USA and Canada would be complete without a mention of Groundhog Day.