The Hautes Alpes region, known as the Southern French Alps, sits in between the Mediterranean and Alpine climate zones and as such has the best weather in France - if you like sun of course!! The region benefits from 300 days of sunshine every year.
It is a mountainous region between 800 and 4000 metres so altitude plays a part in the local weather. The rule of thumb as you climb higher into the mountains is that it gets 1 degree cooler every 100 metres.
This is true throughout the year but there are also other factors such as temperature inversions and winds that influence the microclimate. The sun plays a very important role too so in the winter when the sun is lower in the sky some lower or north facing valleys are blocked from the sun by mountains for a large part of the day so are colder. These valleys are usually where the best cross country skiing is!
There are four well defined seasons:
In April the snow starts to melt and by May the spring flowers are starting to appear. The weather in May can be a bit unpredictable, some rain, sometimes even some snow interspersed with hot sunny days. However, it is a very pretty time to come as the spring flowers start to appear.
June is a fantastic month to visit, the weather has usually settled down so you generally get clear sunny days but it's not too hot. The spring flowers are well established and it's also the month with the longest days!
It can be very hot in the summer up to 35 degrees centigrade, but you have the benefit of altitude and mountain fresh air so it doesn't feel at all claustrophobic. In fact it is very pleasant and you can always cool off in the rivers and lakes. The weather also cools itself down with the occasional mighty thunder storm, which are very spectacular!
By September it is starting to cool down but is still a perfect temperature for outdoor activities. October starts to get colder and the autumn colours here are spectacular. You very often get beautiful clear blue skies and cool crisp air - perfect conditions for walking or mountain biking in the mountains and seeing all the colours.
November can be cold and sometimes rainy, but again you also get the clear blue skies and crisp air. It's usually when the first snow arrives.
The autumn in the Alps is also hunting season which is very different to the UK hunting scene. It is not uncommon to be walking in the Alps in winter and stumble across a stalker hidden in the undergrowth or to see 4X4s with several orange jacketed men with rifles hanging around on first pistes. As such it is advisable to wear high visibility clothing when out and about in autumn.
The snow usually starts to fall in November and stays until the end of April, with more snow the higher up you go. It's not usually until the middle or end of December that there is enough of a base layer for it to stay and this also depends on altitude. Some of the lower valleys below 1000m the snow comes and goes throughout the season. Snowfall is also quite fickle and some years have more snow than others!!
Most of the ski stations have snow canons though so Christmas skiing is guaranteed.
The coldest month is generally January - it's also the month with the best snow! The coldest day last winter was -20 degrees centigrade but it's a dry cold so doesn't get into your bones as much as a damp cold.
Have a look at the current local weather. It is for Orcieres which is the main ski resprt at the end of the valley. It is also good to look at Gap, Embrun and Briancon which are nearby to get a good feel for the weather here. You just type in the city names in the search.
You can also look at the general climate trends for Gap, Orcieres and other villages in the Hautes Alpes