Madeira's weather and climate bears some similarity to the nearby Canary Islands. Madeira has a subtropical climate with an average annual temperature of 22 degrees centigrade - mild indeed, and milder than the Portuguese mainland average temperature. Temperatures rarely fall below 16 degrees centigrade on Madeira. Madeira benefits from both the warming effects of the Gulf Stream which keeps sea temperatures high and from its far south location.
Like the Canary Islands, particularly La Palma and La Gomera, Madeira has a microclimate influenced by its mountainous terrain. You could be simultaneously basking in sunshine in lowlying Funchal, whilst the interior peaks are shrouded in cloud and mist. Rainfall in Madeira is generally experienced to the north (around 4 times higher annually than Funchal). You can expect rain though on Madeira particularly from October to May.
Funchal and the south coast of Madeira generally sees the best of the weather, hence the location down here of main Madeira resort bases around Canico and Calheta, as well as Funchal and the hotel cliff zone.
Madeira experiences a phenomena called capacete - essentially a blanket of cloud which hovers over the coast, then moves inland over the mountains come mid afternoon. La Palma, one of the Canary Islands experiences something similar!
This tends to hit during the months of February, March and June, and can be a tad annoying if you're having a sunbathing day. Another phenomena to hit Madeira for a few days in peak summer months, also experienced on the Canaries, is the North African desert weather which brings very high temperatures of upto 40 degrees centrigrade, and desert dust. Alongside this humidity levels sink low! This can be a hazard for activity holidays on Madeira, trekking and so forth.
Madeira's minimum and maximum average annual temperatures (in degrees centigrade) are as follows,
January - Min 13/Max 19, February - Min 13/Max 18, March - Min 13/Max 19, April - Min 14/Max 19, May - Min 16/Max 21, June - Min 17/Max 22, July - Min 19/Max 24, August - Min 19/Max 24, September - Min 19/Max 24, October - Min 18/Max 23, November - Min 16/Max 22, December - Min 14/Max 19.
Hours of sunshine on Madeira are long, and as follows on average annually, Jan 5 hours, Feb 6 hours, March 6 hours, April 7 hours, May 7 hours, June 7 hours, July 8 hours, August 8 hours, September 8 hours, October 7 hours, November 5 hours, December 5 hours.