A First Real Taste of the Summer Dry Season in 2012

High pressure built in on Friday and Saturday, 11-12 May 2012, bringing with it dry and relatively sunny weather. With limited large-scale circulation in the Vancouver Metro area, pollution, pollen and other particulates quickly contributed to a haze that obscured distant objects, such as the under-construction Port Mann Bridge seen here. Photo taken from Minnekhada Regional Park near Coquitlam, BC, 12 May 2012.

11:55 PDT: Despite an upper trough that is currently passing through the region, the weather continues sunny and relatively warm, though for much of yesterday high clouds obscured the sky. At Vancouver International, W to WNW sea breezes, triggered by higher surface heating over land than over the cool Georgia Strait, have dominated during the warm spell, typically peaking in the afternoon and early evening, with speeds of 17-30 km/h (9-16 kt). The onshore wind has had the effect of keeping the airport temperature readings much lower than places inland. Indeed, even locations only a few km from the shore tend to report significantly warmer readings than along the runways of Vancouver International.

In any event, with the bright sun high in the powder blue sky, a general and persistent lack of precipitation and comfortable temperatures outdoors throughout much of Cascadia, it has been real easy to think Summer has arrived. In fact, some places in the southern part of the region have had temperatures that could be described of as hot.

High pressure aloft left skies clear from southern California all the way into the central British Columbia interior, as shown in this visible satellite image taken at 1730 PDT on 13 May 2012. A Pacific frontal system, stalled by the high pressure ridge, can be seen streaming into Haida Gwaii and southern Alaska, missing Cascadia entirely. Image courtesy of the NOAA National Weather Service.

Here are some high temps from Saturday through Tuesday, capturing the first part of this spring heat-wave:

High Temperatures ºC or (ºF) Mid-May 2012 Warm and Dry Spell
Location	12 May	13 May	14 May	15 May
Comox	17.4 (63)	22.6 (73)	22.8 (73)	23.5 (74)
Vancouver	18.3 (65)	18.6 (65)	18.9 (66)	17.3 (63)
Abbotsford	25.5 (78)	26.4 (80)	27.1 (81)	18.9 (66)
Victoria	21.6 (71)	22.1 (72)	23.8 (75)	18.7 (66)
Bellingham	22.8 (73)	23.3 (74)	23.3 (74)	21.1 (70)
Everett	21.1 (70)	21.7 (71)	23.3 (74)	21.7 (71)
Sea-Tac	24.4 (76)	25.5 (78)	26.7 (80)	24.4 (76)
Olympia	26.1 (79)	27.8 (82)	29.4 (85)	25.5 (78)
Portland	28.9 (84)	30.6 (87)	31.1 (88)	25.5 (78)
Salem	28.3 (83)	30.6 (87)	26.7 (80)	26.1 (79)
Eugene	26.1 (79)	28.3 (83)	21.1 (70)	23.9 (75)
Medford	31.7 (89)	35.0 (95)	28.3 (83)	31.1 (88)
Redding	35.0 (95)	34.4 (94)	25.5 (78)	29.4 (85)
Tofino	19.3 (67)	21.5 (71)	23.3 (74)	17 (63)
Quillayute	23.9 (75)	24.4 (76)	25.5 (78)	21.1 (70)
Hoquiam	24.4 (76)	24.4 (76)	22.8 (73)	21.1 (70)
Astoria	24.4 (76)	23.3 (74)	14.4 (58)	17.8 (64)
Arcata	13.3 (56)	11.7 (53)	15.0 (59)	13.3 (56)

A decent onshore push cooled off coastal stations on Monday, and also invaded parts of the Willamette Valley. Arcata, in typical fashion, missed the heat wave entirely and remained under a cool marine layer with plenty of low clouds and fog. The strong contrast in temperature between Vancouver and Abbotsford is also a common outcome and, as noted above, reflects the cooling power of the still winter-chilled waters of the Georgia Strait.

The dry weather is expected by forecasters to continue through Saturday, though an upper trough could bring a little precipitation late on Thursday. Rain may return on Sunday, at least in the north section, heralding a sustained period of cooler, damp weather for next week. 

Not just humans, but many creatures appeared to enjoy the spell of warm, dry weather. Here a Margined White Butterfly (Pieris marginalia) sips nectar under the warming light of the sun at Minnekhada Regional Park on 12 May 2012.