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 2024-11-01.

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% 3 8% 5% 5% 5% 4 6% 8% 36%	101891
	Night	7% 9% 4 9% 6% 5% 5% 4 7% 8% 36%	97147
Transparency	Day	43% 5% 15% 24% 10% 2	101637
	Night	43% 5% 15% 23% 11% 2	97047
Seeing	Day	14% 10% 29% 29% 14% 4	15363
	Night	11% 8% 32% 33% 13% 2	24375

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% 12% 6% 5% 5% 5% 7% 9% 35%	2219
	11th to 20th	Day	3 9% 4 11% 6% 6% 6% 6% 9% 8% 33%	2232
	21st to end	Day	4 8% 3 9% 6% 6% 6% 5% 6% 9% 39%	2794
February	1st to 10th	Day	3 13% 5% 12% 7% 6% 7% 4 7% 8% 28%	1520
	11th to 20th	Day	6% 10% 4 11% 8% 6% 7% 5% 7% 7% 29%	1647
	21st to end	Day	4 12% 6% 12% 6% 6% 6% 5% 7% 8% 29%	1527
March	1st to 10th	Day	2 11% 4 13% 7% 7% 8% 4 6% 7% 30%	3138
	11th to 20th	Day	6% 11% 2 6% 4 4 5% 4 7% 9% 43%	3448
	21st to end	Day	8% 23% 7% 12% 5% 5% 4 3 5% 5% 23%	3884
April	1st to 10th	Day	7% 17% 5% 12% 5% 5% 5% 5% 6% 8% 26%	2332
	11th to 20th	Day	10% 15% 4 9% 7% 5% 4 5% 6% 7% 28%	2440
	21st to end	Day	12% 13% 4 8% 6% 5% 4 4 6% 8% 29%	2470
May	1st to 10th	Day	17% 15% 4 8% 5% 5% 5% 4 5% 6% 28%	4367
	11th to 20th	Day	11% 9% 4 9% 6% 6% 6% 5% 7% 9% 29%	4694
	21st to end	Day	17% 10% 3 10% 7% 7% 6% 5% 6% 6% 23%	5161
June	1st to 10th	Day	17% 7% 3 8% 6% 5% 6% 5% 8% 8% 27%	2850
	11th to 20th	Day	19% 10% 3 9% 5% 5% 6% 5% 7% 7% 24%	2850
	21st to end	Day	8% 5% 2 7% 6% 6% 6% 4 7% 9% 39%	2850
July	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 5% 7% 9% 45%	4740
	11th to 20th	Day	8% 3 2 4 3 4 5% 5% 8% 11% 48%	4740
	21st to end	Day	4 3 2 5% 4 4 5% 4 6% 10% 54%	5027
August	1st to 10th	Day	9% 6% 2 6% 4 5% 6% 5% 7% 9% 42%	4401
	11th to 20th	Day	7% 5% 2 5% 5% 4 5% 5% 8% 11% 43%	4086
	21st to end	Day	9% 4 1 5% 3 4 4 3 6% 8% 51%	4521
September	1st to 10th	Day	10% 6% 3 6% 4 4 4 3 5% 8% 48%	2359
	11th to 20th	Day	15% 8% 2 5% 4 3 5% 3 6% 7% 42%	2090
	21st to end	Day	9% 8% 3 7% 4 4 4 4 6% 8% 43%	2090
October	1st to 10th	Day	11% 10% 3 8% 4 4 4 3 6% 7% 39%	2009
	11th to 20th	Day	9% 9% 3 8% 4 5% 5% 4 5% 9% 37%	1752
	21st to end	Day	7% 10% 4 8% 7% 5% 5% 5% 6% 7% 37%	1881
November	1st to 10th	Day	7% 16% 5% 9% 5% 5% 5% 4 5% 8% 30%	1549
	11th to 20th	Day	5% 12% 3 8% 6% 5% 5% 4 7% 8% 38%	1439
	21st to end	Day	4 13% 4 9% 5% 4 4 4 8% 10% 36%	1330
December	1st to 10th	Day	4 13% 4 11% 6% 6% 5% 5% 6% 6% 33%	1330
	11th to 20th	Day	3 11% 5% 12% 7% 6% 6% 5% 7% 7% 30%	1682
	21st to end	Day	2 9% 4 9% 5% 5% 6% 4 6% 8% 43%	2442
January	1st to 10th	Night	3 12% 5% 12% 7% 7% 7% 5% 8% 8% 26%	4726
	11th to 20th	Night	3 8% 5% 14% 6% 5% 6% 6% 7% 7% 33%	4695
	21st to end	Night	3 11% 4 10% 6% 6% 5% 4 7% 8% 36%	4862
February	1st to 10th	Night	4 10% 5% 11% 7% 7% 6% 5% 5% 8% 31%	2660
	11th to 20th	Night	5% 11% 6% 11% 6% 5% 6% 5% 7% 8% 30%	2418
	21st to end	Night	2 11% 5% 11% 8% 5% 6% 4 6% 8% 33%	1927
March	1st to 10th	Night	2 9% 5% 15% 8% 7% 7% 6% 6% 8% 27%	3736
	11th to 20th	Night	6% 8% 2 6% 4 5% 5% 5% 7% 9% 44%	3531
	21st to end	Night	8% 20% 6% 16% 7% 5% 4 4 5% 6% 19%	3767
April	1st to 10th	Night	8% 14% 3 11% 6% 5% 5% 5% 7% 8% 28%	1847
	11th to 20th	Night	10% 12% 6% 11% 5% 5% 5% 5% 5% 7% 29%	1691
	21st to end	Night	11% 11% 5% 8% 6% 5% 5% 5% 6% 8% 30%	1710
May	1st to 10th	Night	16% 15% 4 8% 5% 5% 4 4 5% 6% 29%	2596
	11th to 20th	Night	9% 7% 3 7% 6% 5% 6% 5% 8% 10% 34%	2199
	21st to end	Night	14% 10% 3 10% 7% 6% 7% 6% 7% 7% 24%	2414
June	1st to 10th	Night	16% 8% 3 8% 6% 4 5% 5% 6% 6% 33%	1330
	11th to 20th	Night	18% 8% 4 6% 6% 5% 6% 5% 6% 7% 29%	1330
	21st to end	Night	8% 5% 3 6% 5% 6% 6% 4 8% 9% 41%	1330
July	1st to 10th	Night	6% 5% 2 6% 5% 5% 6% 4 7% 8% 46%	2220
	11th to 20th	Night	6% 3 2 5% 4 5% 5% 5% 10% 10% 46%	2220
	21st to end	Night	4 4 1 5% 4 4 4 4 5% 8% 55%	2521
August	1st to 10th	Night	9% 6% 2 7% 4 4 5% 4 7% 9% 43%	2529
	11th to 20th	Night	7% 4 2 7% 5% 4 6% 4 8% 12% 43%	2751
	21st to end	Night	8% 4 1 6% 4 3 3 3 6% 9% 52%	3146
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 3 6% 8% 48%	1816
	11th to 20th	Night	14% 6% 2 5% 3 4 3 3 5% 8% 46%	2090
	21st to end	Night	10% 7% 2 5% 4 4 4 4 7% 8% 45%	2090
October	1st to 10th	Night	9% 9% 3 7% 5% 4 4 4 6% 8% 41%	2171
	11th to 20th	Night	7% 9% 3 6% 4 5% 5% 4 6% 8% 41%	2427
	21st to end	Night	7% 10% 4 8% 5% 5% 5% 5% 7% 8% 36%	2717
November	1st to 10th	Night	8% 13% 5% 8% 5% 4 5% 4 5% 8% 35%	2516
	11th to 20th	Night	3 11% 4 8% 6% 6% 5% 5% 6% 8% 38%	2740
	21st to end	Night	4 11% 4 8% 5% 5% 5% 4 7% 9% 37%	2850
December	1st to 10th	Night	4 11% 4 11% 6% 6% 5% 4 6% 7% 34%	2850
	11th to 20th	Night	2 9% 4 11% 8% 6% 6% 5% 7% 9% 33%	3510
	21st to end	Night	3 8% 4 9% 6% 5% 5% 5% 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	50% 5% 12% 20% 12% 1	1527
March	1st to 10th	Day	48% 8% 14% 16% 11% 1	3138
	11th to 20th	Day	35% 5% 17% 27% 13% 1	3449
	21st to end	Day	61% 5% 13% 14% 6% 1	3884
April	1st to 10th	Day	55% 6% 14% 17% 8% 1	2332
	11th to 20th	Day	54% 6% 11% 20% 9% 1	2440
	21st to end	Day	52% 5% 14% 20% 8% 1	2470
May	1st to 10th	Day	57% 3 12% 23% 5%	4367
	11th to 20th	Day	46% 7% 14% 23% 9%	4698
	21st to end	Day	58% 5% 14% 15% 6% 1	5162
June	1st to 10th	Day	51% 6% 15% 18% 8% 1	2850
	11th to 20th	Day	56% 6% 15% 16% 7% 2	2850
	21st to end	Day	38% 7% 20% 25% 9% 2	2850
July	1st to 10th	Day	32% 6% 16% 26% 16% 4	4666
	11th to 20th	Day	28% 6% 20% 34% 10% 1	4659
	21st to end	Day	25% 5% 14% 29% 22% 5%	4868
August	1st to 10th	Day	36% 5% 18% 34% 6% 1	4384
	11th to 20th	Day	32% 6% 26% 28% 6% 1	4126
	21st to end	Day	31% 4 21% 33% 11% 1	4520
September	1st to 10th	Day	35% 4 17% 26% 14% 5%	2359
	11th to 20th	Day	41% 4 15% 26% 12% 2	2090
	21st to end	Day	39% 5% 14% 27% 12% 3	2090
October	1st to 10th	Day	44% 5% 15% 26% 9% 1	2009
	11th to 20th	Day	42% 5% 16% 25% 9% 3	1752
	21st to end	Day	44% 6% 13% 25% 12% 1	1881
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% 11% 23% 14% 2	1927
March	1st to 10th	Night	51% 7% 11% 20% 10% 1	3736
	11th to 20th	Night	34% 9% 18% 23% 15% 1	3531
	21st to end	Night	65% 5% 12% 14% 5% 1	3767
April	1st to 10th	Night	50% 6% 13% 20% 11% 1	1847
	11th to 20th	Night	53% 4 11% 21% 9% 1	1691
	21st to end	Night	49% 5% 14% 21% 8% 2	1710
May	1st to 10th	Night	55% 5% 12% 21% 7%	2596
	11th to 20th	Night	40% 6% 15% 29% 10% 1	2199
	21st to end	Night	55% 7% 15% 16% 6% 1	2414
June	1st to 10th	Night	49% 5% 16% 19% 10% 1	1330
	11th to 20th	Night	51% 6% 15% 17% 7% 3	1330
	21st to end	Night	37% 6% 23% 25% 8% 1	1330
July	1st to 10th	Night	33% 6% 16% 24% 18% 3	2185
	11th to 20th	Night	28% 6% 22% 31% 9% 4	2178
	21st to end	Night	26% 6% 12% 32% 20% 4	2441
August	1st to 10th	Night	35% 5% 16% 33% 11% 1	2521
	11th to 20th	Night	33% 6% 26% 27% 8% 1	2777
	21st to end	Night	28% 5% 22% 33% 11% 2	3146
September	1st to 10th	Night	35% 4 15% 26% 15% 5%	1816
	11th to 20th	Night	38% 4 16% 26% 12% 4	2090
	21st to end	Night	35% 5% 18% 25% 14% 4	2090
October	1st to 10th	Night	41% 5% 15% 25% 13% 2	2171
	11th to 20th	Night	39% 6% 16% 25% 12% 3	2427
	21st to end	Night	43% 6% 14% 25% 11% 1	2717
November	1st to 10th	Night	47% 5% 13% 22% 11% 2	2516
	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	9% 15% 35% 28% 9% 3	460
	11th to 20th	Day	10% 14% 34% 27% 11% 3	460
	21st to end	Day	16% 16% 34% 21% 9% 5%	506
April	1st to 10th	Day	16% 17% 35% 23% 8% 1	460
	11th to 20th	Day	15% 12% 32% 27% 11% 2	452
	21st to end	Day	21% 15% 25% 27% 11% 2	460
May	1st to 10th	Day	22% 11% 24% 25% 15% 3	510
	11th to 20th	Day	18% 8% 24% 30% 16% 5%	675
	21st to end	Day	19% 9% 20% 29% 19% 4	734
June	1st to 10th	Day	18% 9% 29% 29% 12% 3	680
	11th to 20th	Day	23% 10% 25% 27% 13% 3	680
	21st to end	Day	11% 6% 27% 32% 19% 5%	680
July	1st to 10th	Day	12% 5% 23% 36% 20% 4	671
	11th to 20th	Day	13% 5% 26% 31% 22% 3	668
	21st to end	Day	5% 6% 27% 36% 19% 6%	677
August	1st to 10th	Day	14% 6% 24% 32% 19% 5%	487
	11th to 20th	Day	10% 4 26% 36% 20% 5%	477
	21st to end	Day	11% 9% 23% 31% 19% 7%	539
September	1st to 10th	Day	13% 9% 30% 28% 14% 6%	490
	11th to 20th	Day	20% 7% 25% 29% 15% 5%	490
	21st to end	Day	14% 15% 31% 28% 9% 3	490
October	1st to 10th	Day	17% 8% 31% 27% 14% 4	409
	11th to 20th	Day	11% 13% 35% 27% 11% 3	300
	21st to end	Day	15% 14% 36% 24% 9% 2	330
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% 32% 29% 18% 4	628
March	1st to 10th	Night	8% 8% 36% 34% 12% 3	760
	11th to 20th	Night	9% 8% 36% 34% 11% 2	760
	21st to end	Night	13% 7% 30% 36% 12% 3	836
April	1st to 10th	Night	13% 8% 32% 32% 15% 1	707
	11th to 20th	Night	16% 7% 34% 33% 10%	563
	21st to end	Night	16% 8% 31% 35% 10%	570
May	1st to 10th	Night	17% 11% 27% 30% 14% 1	470
	11th to 20th	Night	13% 7% 29% 37% 13% 1	374
	21st to end	Night	22% 5% 22% 33% 17%	411
June	1st to 10th	Night	21% 6% 29% 29% 14% 1	380
	11th to 20th	Night	21% 4 28% 33% 12% 1	380
	21st to end	Night	11% 3 22% 46% 17% 1	380
July	1st to 10th	Night	10% 4 18% 41% 26% 1	370
	11th to 20th	Night	13% 3 23% 39% 20% 2	368
	21st to end	Night	5% 5% 20% 44% 24% 2	416
August	1st to 10th	Night	12% 3 13% 42% 28% 2	378
	11th to 20th	Night	9% 2 20% 44% 22% 2	528
	21st to end	Night	11% 4 22% 41% 22% 1	627
September	1st to 10th	Night	14% 4 23% 38% 18% 2	665
	11th to 20th	Night	16% 5% 21% 38% 18% 2	760
	21st to end	Night	13% 6% 31% 33% 14% 2	760
October	1st to 10th	Night	14% 7% 29% 33% 15% 2	760
	11th to 20th	Night	12% 6% 34% 33% 13% 2	760
	21st to end	Night	12% 9% 33% 36% 9% 1	836
November	1st to 10th	Night	14% 11% 36% 28% 9% 1	847
	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 2024-10-29 09:20:46. Version ac07

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