Airdrie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Airdrie clear sky chart from 2005-11-06 to 2024-03-01.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	9% 9% 4 7% 6% 4 6% 6% 6% 8% 36%	77918
	Night	7% 9% 4 8% 7% 4 5% 6% 6% 8% 36%	81451
Transparency	Day	44% 5% 16% 23% 10% 2	77624
	Night	44% 5% 15% 23% 11% 2	81325
Seeing	Day	14% 10% 29% 29% 14% 4	14329
	Night	11% 8% 32% 33% 13% 2	23646

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	3 8% 6% 11% 7% 4 5% 5% 7% 9% 35%	2219
	11th to 20th	Day	3 8% 4 10% 8% 5% 6% 8% 9% 8% 33%	2232
	21st to end	Day	4 7% 3 8% 7% 5% 6% 6% 6% 9% 39%	2794
February	1st to 10th	Day	4 11% 6% 9% 9% 4 7% 6% 7% 8% 29%	1520
	11th to 20th	Day	6% 9% 5% 9% 10% 5% 7% 6% 7% 7% 29%	1647
	21st to end	Day	4 10% 7% 11% 7% 4 6% 6% 7% 9% 29%	1527
March	1st to 10th	Day	3 12% 5% 11% 9% 5% 6% 5% 6% 8% 30%	1801
	11th to 20th	Day	5% 11% 5% 7% 6% 4 7% 6% 8% 9% 34%	1951
	21st to end	Day	8% 15% 6% 9% 7% 4 6% 5% 6% 7% 27%	2212
April	1st to 10th	Day	8% 15% 6% 11% 6% 4 6% 6% 6% 8% 25%	2209
	11th to 20th	Day	11% 15% 5% 8% 8% 4 5% 5% 5% 7% 28%	2310
	21st to end	Day	12% 12% 5% 7% 6% 4 5% 5% 5% 8% 30%	2340
May	1st to 10th	Day	13% 11% 5% 8% 7% 4 5% 6% 6% 8% 27%	2477
	11th to 20th	Day	12% 8% 3 6% 6% 4 6% 6% 6% 8% 34%	2654
	21st to end	Day	20% 8% 3 6% 7% 4 5% 5% 6% 7% 28%	2917
June	1st to 10th	Day	18% 7% 3 7% 7% 3 7% 6% 7% 8% 27%	2700
	11th to 20th	Day	20% 9% 3 8% 6% 4 6% 6% 6% 7% 24%	2700
	21st to end	Day	8% 4 3 6% 6% 4 7% 5% 7% 9% 39%	2700
July	1st to 10th	Day	10% 5% 2 6% 7% 4 6% 6% 6% 9% 39%	2700
	11th to 20th	Day	11% 4 2 4 4 3 6% 6% 8% 9% 42%	2700
	21st to end	Day	6% 3 2 4 4 3 5% 5% 7% 10% 50%	2880
August	1st to 10th	Day	11% 5% 1 4 5% 3 5% 5% 6% 9% 44%	2507
	11th to 20th	Day	9% 5% 2 4 4 3 5% 5% 6% 9% 48%	2333
	21st to end	Day	10% 4 2 5% 5% 3 5% 5% 6% 8% 47%	2574
September	1st to 10th	Day	11% 6% 3 5% 5% 3 4 4 5% 7% 48%	2236
	11th to 20th	Day	14% 8% 3 5% 4 3 4 4 6% 7% 43%	1980
	21st to end	Day	10% 8% 3 6% 5% 3 4 5% 5% 7% 43%	1980
October	1st to 10th	Day	12% 10% 4 7% 5% 3 5% 4 6% 6% 39%	1904
	11th to 20th	Day	9% 9% 3 7% 5% 4 5% 4 5% 9% 37%	1660
	21st to end	Day	8% 10% 4 7% 8% 4 5% 7% 6% 7% 36%	1782
November	1st to 10th	Day	8% 14% 6% 8% 6% 4 5% 5% 5% 8% 30%	1549
	11th to 20th	Day	5% 11% 4 6% 7% 4 5% 5% 6% 8% 38%	1439
	21st to end	Day	5% 11% 5% 8% 5% 3 5% 5% 8% 10% 36%	1330
December	1st to 10th	Day	4 12% 5% 11% 7% 4 6% 6% 6% 7% 33%	1330
	11th to 20th	Day	3 11% 5% 10% 8% 5% 7% 7% 6% 7% 31%	1682
	21st to end	Day	3 8% 4 7% 6% 4 5% 5% 6% 8% 43%	2442
January	1st to 10th	Night	3 12% 5% 11% 8% 5% 7% 6% 7% 9% 26%	4726
	11th to 20th	Night	3 8% 5% 13% 7% 4 6% 8% 7% 7% 33%	4695
	21st to end	Night	3 10% 4 8% 7% 4 6% 6% 6% 8% 37%	4862
February	1st to 10th	Night	4 9% 6% 10% 9% 6% 6% 6% 5% 8% 31%	2660
	11th to 20th	Night	5% 11% 6% 9% 7% 4 6% 6% 7% 8% 30%	2418
	21st to end	Night	2 10% 6% 10% 9% 4 6% 5% 6% 8% 34%	1927
March	1st to 10th	Night	4 9% 6% 10% 9% 5% 6% 6% 7% 9% 29%	2165
	11th to 20th	Night	5% 10% 5% 7% 7% 4 6% 6% 7% 9% 34%	2008
	21st to end	Night	7% 13% 6% 9% 8% 3 5% 6% 7% 9% 27%	2142
April	1st to 10th	Night	8% 12% 4 10% 7% 4 5% 6% 7% 8% 28%	1750
	11th to 20th	Night	11% 12% 6% 10% 6% 3 5% 6% 5% 7% 29%	1601
	21st to end	Night	12% 10% 5% 7% 7% 3 5% 6% 6% 9% 30%	1620
May	1st to 10th	Night	11% 12% 4 7% 6% 4 6% 5% 6% 7% 33%	1482
	11th to 20th	Night	11% 6% 3 6% 7% 3 5% 4 6% 8% 41%	1239
	21st to end	Night	17% 7% 3 5% 6% 3 7% 7% 6% 9% 29%	1358
June	1st to 10th	Night	17% 7% 4 7% 6% 3 5% 6% 6% 7% 32%	1260
	11th to 20th	Night	19% 6% 5% 5% 7% 3 6% 7% 7% 7% 29%	1260
	21st to end	Night	8% 5% 3 5% 6% 4 7% 5% 8% 9% 41%	1260
July	1st to 10th	Night	8% 4 2 5% 6% 3 6% 6% 6% 11% 43%	1260
	11th to 20th	Night	10% 4 2 5% 5% 4 6% 6% 8% 8% 41%	1260
	21st to end	Night	5% 4 2 5% 4 3 3 5% 6% 10% 55%	1433
August	1st to 10th	Night	10% 4 2 6% 4 4 4 5% 7% 9% 45%	1432
	11th to 20th	Night	8% 4 1 4 5% 2 4 5% 7% 11% 48%	1568
	21st to end	Night	9% 4 2 5% 4 2 3 4 6% 9% 51%	1782
September	1st to 10th	Night	11% 6% 2 5% 5% 3 4 4 5% 8% 46%	1720
	11th to 20th	Night	13% 6% 2 4 4 3 3 4 5% 8% 46%	1980
	21st to end	Night	10% 7% 2 4 5% 3 4 5% 6% 8% 44%	1980
October	1st to 10th	Night	10% 9% 3 7% 6% 3 4 5% 6% 7% 40%	2056
	11th to 20th	Night	8% 9% 3 6% 5% 4 5% 6% 6% 8% 40%	2299
	21st to end	Night	7% 10% 5% 8% 6% 4 5% 6% 7% 8% 35%	2574
November	1st to 10th	Night	8% 13% 5% 7% 5% 3 5% 5% 6% 7% 35%	2510
	11th to 20th	Night	4 10% 4 7% 7% 4 5% 6% 6% 8% 38%	2740
	21st to end	Night	4 10% 5% 7% 6% 4 5% 6% 7% 9% 37%	2850
December	1st to 10th	Night	5% 10% 5% 10% 7% 4 6% 6% 6% 8% 34%	2850
	11th to 20th	Night	2 9% 5% 10% 9% 5% 6% 6% 7% 9% 33%	3510
	21st to end	Night	3 8% 4 8% 7% 4 5% 6% 6% 7% 43%	5214

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	43% 5% 13% 25% 12% 3	2219
	11th to 20th	Day	45% 6% 10% 16% 18% 5%	2253
	21st to end	Day	40% 6% 15% 30% 9% 1	2794
February	1st to 10th	Day	51% 6% 14% 17% 9% 2	1520
	11th to 20th	Day	50% 5% 13% 21% 9% 2	1656
	21st to end	Day	51% 5% 11% 20% 12% 1	1527
March	1st to 10th	Day	50% 7% 16% 18% 8% 1	1801
	11th to 20th	Day	44% 6% 14% 23% 11% 2	1952
	21st to end	Day	55% 5% 15% 17% 6% 1	2212
April	1st to 10th	Day	55% 6% 14% 17% 8% 1	2209
	11th to 20th	Day	55% 5% 10% 19% 9% 1	2310
	21st to end	Day	52% 5% 14% 20% 8% 1	2340
May	1st to 10th	Day	54% 4 15% 20% 7% 1	2477
	11th to 20th	Day	44% 5% 16% 24% 10% 1	2658
	21st to end	Day	53% 5% 14% 21% 6% 1	2918
June	1st to 10th	Day	52% 5% 16% 19% 7% 1	2700
	11th to 20th	Day	56% 6% 15% 16% 6% 2	2700
	21st to end	Day	38% 7% 20% 25% 8% 2	2700
July	1st to 10th	Day	39% 7% 19% 24% 10% 2	2626
	11th to 20th	Day	36% 7% 21% 26% 9% 1	2619
	21st to end	Day	27% 6% 20% 32% 13% 1	2720
August	1st to 10th	Day	35% 6% 21% 28% 8% 1	2490
	11th to 20th	Day	32% 5% 24% 28% 9% 2	2333
	21st to end	Day	33% 4 20% 29% 11% 2	2574
September	1st to 10th	Day	36% 4 17% 26% 13% 4	2236
	11th to 20th	Day	41% 4 15% 27% 12% 2	1980
	21st to end	Day	40% 5% 14% 26% 12% 3	1980
October	1st to 10th	Day	45% 5% 14% 25% 9% 1	1904
	11th to 20th	Day	43% 5% 15% 26% 9% 2	1660
	21st to end	Day	45% 6% 13% 23% 12% 1	1782
November	1st to 10th	Day	52% 6% 10% 20% 10% 2	1549
	11th to 20th	Day	44% 4 16% 23% 11% 1	1439
	21st to end	Day	42% 5% 18% 23% 10% 2	1330
December	1st to 10th	Day	49% 5% 14% 17% 12% 3	1330
	11th to 20th	Day	49% 4 19% 19% 8% 1	1684
	21st to end	Day	37% 5% 12% 22% 19% 6%	2442
January	1st to 10th	Night	51% 6% 14% 20% 7% 2	4726
	11th to 20th	Night	47% 5% 12% 17% 14% 6%	4736
	21st to end	Night	44% 4 15% 25% 11% 1	4862
February	1st to 10th	Night	51% 5% 11% 19% 11% 3	2660
	11th to 20th	Night	49% 5% 13% 20% 11% 2	2419
	21st to end	Night	46% 5% 10% 23% 14% 2	1927
March	1st to 10th	Night	48% 7% 13% 23% 7% 1	2165
	11th to 20th	Night	45% 6% 14% 20% 13% 1	2008
	21st to end	Night	51% 6% 15% 19% 8% 2	2142
April	1st to 10th	Night	50% 6% 12% 20% 11% 1	1750
	11th to 20th	Night	53% 4 11% 21% 9% 1	1601
	21st to end	Night	49% 4 15% 21% 8% 2	1620
May	1st to 10th	Night	49% 5% 15% 19% 11% 1	1482
	11th to 20th	Night	39% 5% 15% 28% 11% 1	1239
	21st to end	Night	48% 7% 16% 22% 6% 1	1358
June	1st to 10th	Night	49% 4 16% 19% 10%	1260
	11th to 20th	Night	52% 7% 16% 17% 7% 2	1260
	21st to end	Night	37% 6% 23% 26% 7% 1	1260
July	1st to 10th	Night	34% 7% 23% 24% 11% 1	1225
	11th to 20th	Night	37% 7% 21% 23% 11% 1	1218
	21st to end	Night	25% 7% 18% 33% 15% 1	1353
August	1st to 10th	Night	35% 5% 20% 30% 9% 1	1424
	11th to 20th	Night	29% 6% 24% 28% 11% 1	1568
	21st to end	Night	30% 5% 16% 32% 14% 3	1782
September	1st to 10th	Night	36% 4 15% 26% 14% 4	1720
	11th to 20th	Night	37% 4 16% 26% 13% 4	1980
	21st to end	Night	36% 5% 18% 24% 14% 4	1980
October	1st to 10th	Night	42% 5% 14% 25% 12% 2	2056
	11th to 20th	Night	39% 6% 16% 25% 12% 3	2299
	21st to end	Night	44% 7% 14% 24% 11% 1	2574
November	1st to 10th	Night	47% 5% 13% 22% 11% 2	2510
	11th to 20th	Night	42% 5% 16% 21% 14% 1	2740
	21st to end	Night	42% 6% 17% 22% 10% 3	2850
December	1st to 10th	Night	48% 5% 12% 22% 10% 3	2850
	11th to 20th	Night	46% 5% 18% 23% 7% 1	3507
	21st to end	Night	38% 4 12% 25% 14% 6%	5214

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	6% 12% 36% 26% 12% 8%	180
	11th to 20th	Day	9% 10% 39% 26% 13% 2	180
	21st to end	Day	10% 7% 37% 31% 12% 3	198
February	1st to 10th	Day	14% 17% 34% 21% 9% 6%	180
	11th to 20th	Day	8% 13% 40% 28% 10% 2	262
	21st to end	Day	9% 11% 32% 32% 14% 2	339
March	1st to 10th	Day	10% 15% 35% 27% 10% 3	421
	11th to 20th	Day	10% 15% 33% 27% 12% 3	420
	21st to end	Day	16% 16% 34% 20% 10% 5%	462
April	1st to 10th	Day	16% 16% 34% 24% 9% 1	420
	11th to 20th	Day	16% 12% 30% 28% 11% 2	412
	21st to end	Day	21% 14% 25% 27% 11% 2	420
May	1st to 10th	Day	21% 11% 24% 27% 15% 3	467
	11th to 20th	Day	18% 7% 23% 30% 17% 5%	625
	21st to end	Day	19% 8% 20% 29% 19% 4	679
June	1st to 10th	Day	18% 8% 29% 30% 12% 3	630
	11th to 20th	Day	23% 10% 25% 28% 12% 2	630
	21st to end	Day	11% 5% 27% 31% 20% 6%	630
July	1st to 10th	Day	13% 5% 23% 35% 20% 4	621
	11th to 20th	Day	14% 5% 27% 31% 20% 2	618
	21st to end	Day	5% 6% 27% 37% 19% 7%	626
August	1st to 10th	Day	14% 6% 23% 33% 19% 5%	447
	11th to 20th	Day	11% 4 26% 35% 19% 5%	437
	21st to end	Day	11% 9% 23% 31% 20% 7%	495
September	1st to 10th	Day	14% 10% 30% 28% 13% 5%	450
	11th to 20th	Day	19% 8% 24% 29% 15% 5%	450
	21st to end	Day	14% 15% 29% 29% 10% 3	450
October	1st to 10th	Day	18% 8% 30% 25% 14% 4	374
	11th to 20th	Day	13% 13% 33% 27% 11% 3	270
	21st to end	Day	15% 14% 36% 24% 9% 2	297
November	1st to 10th	Day	16% 11% 33% 29% 8% 2	270
	11th to 20th	Day	16% 13% 39% 24% 6% 2	231
	21st to end	Day	8% 12% 38% 26% 11% 6%	180
December	1st to 10th	Day	8% 11% 40% 27% 11% 3	180
	11th to 20th	Day	8% 13% 45% 20% 11% 3	180
	21st to end	Day	7% 10% 35% 28% 17% 3	198
January	1st to 10th	Night	9% 11% 37% 31% 11% 1	950
	11th to 20th	Night	8% 10% 42% 31% 8% 1	946
	21st to end	Night	11% 14% 36% 29% 9% 1	836
February	1st to 10th	Night	9% 12% 33% 30% 12% 3	760
	11th to 20th	Night	9% 9% 37% 33% 11% 2	744
	21st to end	Night	7% 10% 31% 30% 18% 4	628
March	1st to 10th	Night	8% 7% 36% 34% 12% 3	722
	11th to 20th	Night	9% 8% 35% 34% 11% 2	720
	21st to end	Night	13% 7% 30% 35% 13% 3	792
April	1st to 10th	Night	12% 8% 30% 33% 16% 1	670
	11th to 20th	Night	16% 7% 33% 34% 10%	533
	21st to end	Night	16% 8% 31% 35% 10%	540
May	1st to 10th	Night	16% 11% 27% 30% 15% 1	446
	11th to 20th	Night	14% 7% 27% 37% 14% 1	354
	21st to end	Night	21% 5% 22% 34% 17% 1	389
June	1st to 10th	Night	21% 5% 29% 30% 14% 1	360
	11th to 20th	Night	22% 4 27% 34% 12% 1	360
	21st to end	Night	11% 3 21% 46% 18% 1	360
July	1st to 10th	Night	10% 4 17% 41% 27% 1	350
	11th to 20th	Night	13% 3 24% 39% 18% 3	348
	21st to end	Night	5% 5% 20% 44% 24% 2	394
August	1st to 10th	Night	12% 3 14% 41% 28% 2	358
	11th to 20th	Night	10% 2 21% 44% 21% 2	500
	21st to end	Night	11% 4 21% 41% 22% 1	594
September	1st to 10th	Night	15% 4 24% 38% 18% 2	630
	11th to 20th	Night	15% 5% 21% 39% 18% 2	720
	21st to end	Night	14% 6% 31% 32% 15% 2	720
October	1st to 10th	Night	15% 7% 28% 33% 16% 2	720
	11th to 20th	Night	13% 6% 33% 33% 13% 2	720
	21st to end	Night	12% 9% 33% 35% 8% 1	792
November	1st to 10th	Night	14% 11% 36% 28% 9% 1	845
	11th to 20th	Night	9% 12% 46% 25% 7% 1	950
	21st to end	Night	9% 11% 41% 30% 8% 1	950
December	1st to 10th	Night	10% 11% 37% 29% 11% 2	950
	11th to 20th	Night	6% 10% 41% 34% 8% 1	950
	21st to end	Night	9% 10% 37% 32% 9% 2	1045

Page generated at 2024-02-27 04:30:13. Version ac07

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