Fort MacKay/Firebag Aerodrome
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort MacKay/Firebag Aerodrome clear sky chart from 2005-11-06 to 2026-01-02.

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 10% 6% 6% 6% 5% 6% 7% 33%	131402
	Night	7% 10% 4 11% 7% 6% 6% 5% 6% 7% 30%	128559
Transparency	Day	46% 9% 16% 22% 7%	131081
	Night	50% 8% 15% 20% 6%	128460
Seeing	Day	15% 12% 30% 27% 12% 3	17986
	Night	13% 10% 33% 30% 12% 2	26431

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	4 10% 4 18% 11% 10% 10% 6% 7% 4 17%	2264
	11th to 20th	Day	4 10% 4 14% 8% 6% 9% 7% 11% 8% 19%	3042
	21st to end	Day	3 12% 5% 18% 10% 7% 7% 5% 7% 5% 20%	3498
February	1st to 10th	Day	4 10% 5% 12% 8% 9% 10% 7% 7% 8% 21%	1472
	11th to 20th	Day	4 11% 4 12% 7% 9% 8% 7% 5% 5% 29%	1691
	21st to end	Day	2 9% 5% 11% 9% 9% 8% 7% 8% 8% 24%	1485
March	1st to 10th	Day	2 10% 4 12% 8% 7% 9% 6% 7% 8% 26%	4374
	11th to 20th	Day	3 10% 5% 13% 7% 7% 7% 6% 7% 7% 28%	4999
	21st to end	Day	2 9% 5% 13% 7% 6% 5% 3 6% 7% 39%	5525
April	1st to 10th	Day	7% 13% 5% 11% 6% 4 6% 5% 6% 6% 30%	2565
	11th to 20th	Day	8% 12% 4 11% 8% 7% 5% 4 6% 6% 29%	2570
	21st to end	Day	9% 12% 4 11% 7% 5% 5% 5% 6% 7% 28%	2767
May	1st to 10th	Day	10% 10% 4 9% 5% 5% 5% 4 6% 7% 35%	6780
	11th to 20th	Day	15% 11% 3 9% 6% 6% 5% 4 5% 6% 29%	6774
	21st to end	Day	10% 8% 3 8% 5% 5% 6% 5% 6% 8% 37%	7907
June	1st to 10th	Day	16% 9% 3 9% 5% 5% 5% 5% 6% 7% 30%	3386
	11th to 20th	Day	18% 11% 3 8% 6% 4 5% 4 6% 7% 28%	3400
	21st to end	Day	13% 8% 3 7% 6% 5% 6% 5% 7% 8% 33%	3400
July	1st to 10th	Day	10% 5% 2 7% 6% 6% 6% 5% 9% 10% 34%	7700
	11th to 20th	Day	7% 4 2 4 4 4 4 4 6% 8% 54%	7389
	21st to end	Day	13% 5% 2 6% 4 5% 5% 4 6% 8% 42%	7376
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	4870
	11th to 20th	Day	17% 6% 2 6% 4 5% 5% 3 6% 8% 36%	4526
	21st to end	Day	16% 6% 2 7% 4 5% 5% 4 6% 8% 37%	4664
September	1st to 10th	Day	17% 9% 2 8% 4 4 5% 3 5% 7% 36%	2545
	11th to 20th	Day	13% 10% 3 7% 5% 5% 5% 5% 5% 7% 35%	2300
	21st to end	Day	12% 10% 3 8% 5% 5% 4 4 6% 7% 34%	2180
October	1st to 10th	Day	9% 14% 5% 10% 6% 4 5% 4 5% 7% 29%	3270
	11th to 20th	Day	11% 14% 5% 11% 6% 4 3 3 5% 7% 32%	3038
	21st to end	Day	9% 14% 5% 14% 5% 4 3 3 5% 6% 31%	2852
November	1st to 10th	Day	8% 17% 5% 14% 8% 5% 4 3 4 5% 26%	1630
	11th to 20th	Day	10% 12% 6% 15% 11% 6% 6% 3 5% 5% 20%	1397
	21st to end	Day	8% 13% 6% 15% 9% 6% 6% 5% 5% 5% 22%	1260
December	1st to 10th	Day	4 11% 6% 16% 12% 8% 8% 5% 6% 6% 18%	2020
	11th to 20th	Day	7% 15% 6% 13% 7% 6% 9% 5% 4 5% 23%	1945
	21st to end	Day	4 9% 5% 13% 9% 6% 5% 5% 5% 5% 34%	2541
January	1st to 10th	Night	4 10% 5% 15% 9% 7% 7% 6% 7% 8% 21%	7686
	11th to 20th	Night	3 9% 4 12% 8% 7% 8% 9% 11% 7% 23%	6854
	21st to end	Night	3 12% 5% 15% 8% 6% 6% 5% 6% 7% 24%	7458
February	1st to 10th	Night	3 10% 4 11% 8% 9% 9% 6% 7% 6% 25%	2945
	11th to 20th	Night	4 11% 5% 11% 7% 8% 8% 6% 7% 6% 26%	2596
	21st to end	Night	2 8% 5% 14% 10% 8% 7% 5% 9% 7% 26%	2145
March	1st to 10th	Night	2 11% 5% 14% 9% 7% 8% 5% 7% 7% 26%	5507
	11th to 20th	Night	4 12% 6% 11% 6% 7% 7% 4 6% 8% 29%	5000
	21st to end	Night	4 10% 4 12% 7% 4 4 4 6% 6% 39%	5448
April	1st to 10th	Night	10% 11% 4 12% 5% 5% 5% 4 7% 8% 29%	1833
	11th to 20th	Night	7% 11% 5% 10% 6% 6% 6% 4 7% 6% 32%	1781
	21st to end	Night	8% 13% 5% 10% 6% 6% 5% 4 6% 6% 32%	1631
May	1st to 10th	Night	11% 9% 4 8% 5% 5% 6% 4 6% 7% 35%	3180
	11th to 20th	Night	15% 11% 3 6% 5% 6% 6% 4 6% 8% 29%	3118
	21st to end	Night	9% 8% 3 7% 5% 5% 6% 5% 8% 7% 37%	2968
June	1st to 10th	Night	18% 7% 2 7% 5% 5% 5% 4 7% 9% 32%	1010
	11th to 20th	Night	17% 9% 4 7% 6% 6% 4 5% 7% 6% 31%	1000
	21st to end	Night	13% 6% 1 6% 6% 5% 6% 5% 7% 9% 38%	1000
July	1st to 10th	Night	9% 4 2 6% 4 5% 6% 6% 10% 11% 36%	2260
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 8% 62%	2567
	21st to end	Night	12% 4 1 5% 4 4 4 3 6% 9% 47%	3467
August	1st to 10th	Night	9% 4 1 4 4 5% 4 4 6% 8% 51%	2280
	11th to 20th	Night	13% 6% 2 6% 4 5% 5% 4 6% 9% 40%	2511
	21st to end	Night	14% 6% 2 6% 5% 4 5% 5% 5% 8% 41%	3245
September	1st to 10th	Night	15% 8% 3 6% 4 5% 4 4 6% 8% 36%	1855
	11th to 20th	Night	14% 7% 2 7% 4 5% 5% 4 6% 7% 39%	2096
	21st to end	Night	13% 9% 2 7% 4 5% 5% 3 7% 7% 37%	2220
October	1st to 10th	Night	12% 14% 4 7% 5% 4 4 3 5% 6% 36%	3920
	11th to 20th	Night	11% 13% 4 10% 5% 5% 5% 4 6% 7% 32%	4108
	21st to end	Night	10% 16% 6% 14% 7% 6% 5% 4 5% 5% 22%	4916
November	1st to 10th	Night	9% 14% 7% 14% 9% 5% 4 3 5% 5% 25%	2886
	11th to 20th	Night	9% 13% 5% 15% 10% 6% 5% 4 6% 6% 21%	3222
	21st to end	Night	7% 14% 6% 14% 9% 7% 6% 5% 6% 5% 22%	3360
December	1st to 10th	Night	5% 13% 5% 17% 12% 8% 9% 6% 5% 5% 15%	5380
	11th to 20th	Night	5% 13% 6% 15% 9% 8% 9% 5% 6% 6% 18%	6449
	21st to end	Night	3 9% 4 12% 10% 7% 6% 5% 5% 6% 33%	8657

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	65% 8% 10% 13% 4	2264
	11th to 20th	Day	54% 9% 13% 16% 8%	3063
	21st to end	Day	60% 10% 13% 11% 5%	3498
February	1st to 10th	Day	55% 8% 12% 16% 9%	1472
	11th to 20th	Day	53% 7% 15% 18% 7%	1700
	21st to end	Day	52% 9% 13% 19% 7%	1485
March	1st to 10th	Day	49% 9% 15% 22% 4	4374
	11th to 20th	Day	49% 9% 13% 21% 9%	5000
	21st to end	Day	42% 7% 10% 23% 15% 3	5525
April	1st to 10th	Day	50% 9% 12% 18% 10% 1	2565
	11th to 20th	Day	52% 6% 11% 20% 11% 1	2570
	21st to end	Day	50% 8% 11% 23% 7%	2767
May	1st to 10th	Day	45% 7% 15% 21% 12% 1	6780
	11th to 20th	Day	51% 8% 11% 20% 9%	6778
	21st to end	Day	40% 10% 15% 24% 10% 1	7908
June	1st to 10th	Day	50% 8% 12% 19% 11%	3386
	11th to 20th	Day	53% 8% 12% 19% 8%	3400
	21st to end	Day	45% 10% 17% 19% 9% 1	3400
July	1st to 10th	Day	38% 11% 25% 21% 4 1	7616
	11th to 20th	Day	25% 8% 15% 39% 12%	7296
	21st to end	Day	36% 9% 18% 34% 3	7169
August	1st to 10th	Day	32% 10% 17% 37% 4	4852
	11th to 20th	Day	42% 11% 21% 20% 6%	4571
	21st to end	Day	44% 8% 25% 21% 2	4663
September	1st to 10th	Day	46% 9% 20% 19% 5%	2545
	11th to 20th	Day	45% 9% 20% 21% 4	2300
	21st to end	Day	47% 8% 18% 21% 6%	2180
October	1st to 10th	Day	53% 7% 12% 25% 4	3270
	11th to 20th	Day	52% 6% 15% 23% 4	3038
	21st to end	Day	52% 9% 21% 17% 1	2852
November	1st to 10th	Day	60% 7% 13% 17% 3	1630
	11th to 20th	Day	65% 8% 12% 12% 2	1397
	21st to end	Day	61% 10% 13% 12% 4	1260
December	1st to 10th	Day	64% 9% 10% 14% 2	2020
	11th to 20th	Day	61% 7% 14% 13% 5%	1946
	21st to end	Day	49% 7% 18% 22% 5%	2541
January	1st to 10th	Night	57% 8% 15% 16% 3	7686
	11th to 20th	Night	50% 9% 13% 17% 10% 1	6895
	21st to end	Night	56% 9% 17% 11% 6%	7458
February	1st to 10th	Night	54% 8% 14% 16% 9%	2945
	11th to 20th	Night	53% 7% 15% 18% 6%	2597
	21st to end	Night	51% 8% 16% 18% 7%	2145
March	1st to 10th	Night	54% 7% 14% 21% 4	5507
	11th to 20th	Night	48% 10% 12% 23% 7%	5000
	21st to end	Night	42% 7% 10% 21% 18% 1	5448
April	1st to 10th	Night	50% 8% 13% 18% 10% 1	1833
	11th to 20th	Night	48% 7% 12% 17% 14% 2	1781
	21st to end	Night	49% 7% 11% 23% 9% 1	1631
May	1st to 10th	Night	43% 8% 11% 26% 12% 2	3180
	11th to 20th	Night	48% 9% 11% 23% 8%	3118
	21st to end	Night	38% 10% 16% 25% 11%	2968
June	1st to 10th	Night	46% 8% 11% 21% 12%	1010
	11th to 20th	Night	49% 10% 14% 18% 9%	1000
	21st to end	Night	38% 10% 19% 23% 10% 1	1000
July	1st to 10th	Night	35% 12% 26% 23% 4 1	2235
	11th to 20th	Night	21% 7% 14% 46% 11% 1	2537
	21st to end	Night	31% 8% 20% 39% 3	3369
August	1st to 10th	Night	27% 9% 18% 40% 5%	2273
	11th to 20th	Night	37% 11% 23% 22% 7%	2532
	21st to end	Night	39% 9% 29% 21% 2	3245
September	1st to 10th	Night	41% 12% 21% 22% 4	1855
	11th to 20th	Night	42% 10% 17% 24% 7%	2096
	21st to end	Night	44% 9% 17% 22% 8%	2220
October	1st to 10th	Night	47% 6% 14% 26% 7%	3920
	11th to 20th	Night	50% 7% 15% 25% 3	4108
	21st to end	Night	62% 8% 14% 13% 3	4916
November	1st to 10th	Night	61% 7% 13% 15% 3	2886
	11th to 20th	Night	62% 10% 13% 11% 3	3222
	21st to end	Night	61% 9% 14% 12% 3	3360
December	1st to 10th	Night	68% 7% 11% 10% 3	5380
	11th to 20th	Night	63% 9% 13% 12% 2	6447
	21st to end	Night	48% 8% 14% 24% 6%	8657

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	11% 11% 31% 32% 13% 2	202
	11th to 20th	Day	14% 12% 37% 28% 9% 2	200
	21st to end	Day	7% 21% 38% 25% 7% 2	220
February	1st to 10th	Day	8% 12% 39% 27% 14% 2	200
	11th to 20th	Day	9% 12% 34% 30% 15%	267
	21st to end	Day	7% 14% 36% 28% 10% 5%	249
March	1st to 10th	Day	8% 14% 40% 24% 13% 1	397
	11th to 20th	Day	12% 15% 37% 25% 10%	500
	21st to end	Day	9% 17% 33% 29% 11% 2	550
April	1st to 10th	Day	16% 17% 39% 20% 6% 2	500
	11th to 20th	Day	17% 17% 33% 22% 9% 3	492
	21st to end	Day	15% 15% 33% 27% 8% 2	663
May	1st to 10th	Day	15% 13% 30% 25% 13% 3	703
	11th to 20th	Day	15% 11% 26% 31% 16% 1	725
	21st to end	Day	14% 13% 28% 31% 12% 3	789
June	1st to 10th	Day	22% 14% 28% 24% 11% 2	916
	11th to 20th	Day	21% 12% 25% 27% 13% 2	930
	21st to end	Day	14% 9% 24% 33% 18% 3	930
July	1st to 10th	Day	14% 8% 27% 32% 16% 2	916
	11th to 20th	Day	15% 7% 21% 31% 21% 5%	847
	21st to end	Day	16% 8% 24% 29% 18% 5%	794
August	1st to 10th	Day	13% 9% 19% 32% 20% 8%	726
	11th to 20th	Day	16% 11% 30% 28% 12% 3	652
	21st to end	Day	18% 8% 31% 27% 14% 2	583
September	1st to 10th	Day	22% 13% 30% 23% 11% 2	530
	11th to 20th	Day	18% 11% 30% 30% 9% 2	530
	21st to end	Day	20% 17% 31% 23% 8%	510
October	1st to 10th	Day	18% 18% 32% 22% 6% 3	330
	11th to 20th	Day	18% 21% 39% 19% 3	330
	21st to end	Day	19% 14% 37% 23% 6% 1	363
November	1st to 10th	Day	16% 17% 37% 23% 7%	320
	11th to 20th	Day	15% 19% 39% 20% 5% 1	220
	21st to end	Day	14% 12% 42% 25% 6% 1	220
December	1st to 10th	Day	9% 14% 38% 29% 10% 1	220
	11th to 20th	Day	11% 10% 36% 31% 9% 2	220
	21st to end	Day	7% 10% 34% 34% 12% 3	242
January	1st to 10th	Night	10% 12% 37% 27% 12% 1	1107
	11th to 20th	Night	9% 12% 38% 31% 9% 1	1025
	21st to end	Night	13% 14% 38% 27% 7% 1	1100
February	1st to 10th	Night	7% 10% 34% 31% 13% 4	945
	11th to 20th	Night	8% 9% 40% 31% 10% 2	784
	21st to end	Night	5% 10% 36% 34% 14% 1	660
March	1st to 10th	Night	7% 12% 36% 32% 12% 2	800
	11th to 20th	Night	15% 9% 37% 29% 9% 1	800
	21st to end	Night	9% 11% 31% 34% 12% 2	864
April	1st to 10th	Night	13% 11% 37% 27% 11% 2	600
	11th to 20th	Night	12% 10% 32% 33% 12% 1	593
	21st to end	Night	14% 8% 34% 32% 11% 2	595
May	1st to 10th	Night	13% 11% 28% 32% 16% 1	400
	11th to 20th	Night	14% 11% 28% 31% 14% 1	394
	21st to end	Night	13% 8% 26% 38% 11% 4	433
June	1st to 10th	Night	22% 8% 23% 33% 13% 1	400
	11th to 20th	Night	17% 6% 28% 29% 19% 1	400
	21st to end	Night	16% 5% 20% 34% 23% 3	400
July	1st to 10th	Night	11% 5% 25% 37% 21% 1	390
	11th to 20th	Night	10% 4 24% 36% 23% 3	388
	21st to end	Night	13% 3 16% 36% 26% 5%	438
August	1st to 10th	Night	12% 5% 17% 38% 25% 4	398
	11th to 20th	Night	14% 4 27% 36% 19% 1	491
	21st to end	Night	18% 4 25% 33% 18% 1	660
September	1st to 10th	Night	18% 6% 28% 30% 15% 3	600
	11th to 20th	Night	18% 6% 25% 36% 13% 1	696
	21st to end	Night	17% 12% 32% 28% 10%	800
October	1st to 10th	Night	22% 13% 34% 21% 8% 2	800
	11th to 20th	Night	19% 11% 38% 23% 8% 1	800
	21st to end	Night	21% 12% 33% 23% 8% 2	1070
November	1st to 10th	Night	15% 14% 35% 25% 10% 1	1025
	11th to 20th	Night	16% 12% 40% 23% 8% 1	1050
	21st to end	Night	12% 14% 41% 23% 8% 1	1050
December	1st to 10th	Night	10% 13% 36% 32% 9% 1	1050
	11th to 20th	Night	11% 11% 38% 31% 8% 1	1149
	21st to end	Night	10% 9% 34% 30% 14% 2	1276

Page generated at 2025-12-29 23:14:05. Version ac07

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