Taber
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Taber clear sky chart from 2005-11-06 to 2025-02-25.

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	8% 8% 3 7% 5% 4 5% 4 6% 8% 44%	112087
	Night	7% 9% 3 8% 5% 5% 5% 4 6% 8% 41%	115263
Transparency	Day	37% 5% 14% 28% 13% 3	111830
	Night	40% 6% 15% 25% 12% 2	115166
Seeing	Day	13% 10% 27% 28% 18% 5%	15721
	Night	12% 11% 34% 30% 12% 1	25130

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	6% 18% 6% 11% 5% 5% 5% 4 6% 7% 27%	3179
	11th to 20th	Day	5% 11% 5% 9% 5% 6% 8% 5% 6% 5% 34%	3175
	21st to end	Day	2 8% 6% 9% 6% 5% 4 3 6% 8% 44%	4004
February	1st to 10th	Day	7% 14% 4 12% 7% 6% 4 4 6% 6% 29%	1718
	11th to 20th	Day	6% 12% 3 11% 6% 7% 6% 6% 6% 8% 28%	1755
	21st to end	Day	4 11% 5% 11% 8% 5% 5% 4 6% 7% 33%	1506
March	1st to 10th	Day	5% 10% 3 9% 6% 6% 6% 4 7% 8% 37%	3220
	11th to 20th	Day	7% 8% 3 6% 4 4 4 4 5% 9% 46%	3489
	21st to end	Day	10% 15% 5% 10% 6% 5% 5% 4 6% 7% 27%	3825
April	1st to 10th	Day	9% 12% 3 9% 5% 5% 7% 5% 6% 7% 32%	2316
	11th to 20th	Day	11% 12% 3 8% 5% 5% 5% 4 6% 8% 33%	2440
	21st to end	Day	11% 9% 3 7% 6% 4 4 5% 6% 8% 36%	2470
May	1st to 10th	Day	21% 11% 4 6% 4 4 4 3 5% 6% 32%	4238
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 8% 10% 38%	4596
	21st to end	Day	14% 6% 3 7% 5% 5% 6% 5% 7% 8% 34%	5161
June	1st to 10th	Day	12% 5% 3 6% 5% 5% 4 5% 7% 9% 39%	2850
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 5% 7% 9% 33%	2850
	21st to end	Day	7% 4 1 5% 4 4 4 5% 6% 9% 52%	2850
July	1st to 10th	Day	5% 3 1 5% 3 4 4 4 6% 8% 57%	4740
	11th to 20th	Day	4 3 1 3 3 3 3 3 6% 8% 64%	4740
	21st to end	Day	2 2 1 2 2 2 3 3 4 7% 72%	5080
August	1st to 10th	Day	8% 5% 2 4 3 3 4 4 6% 9% 52%	4250
	11th to 20th	Day	5% 3 2 5% 4 4 4 4 6% 8% 56%	4028
	21st to end	Day	8% 3 1 3 3 3 3 3 5% 7% 60%	4521
September	1st to 10th	Day	10% 4 2 4 3 3 3 2 5% 6% 58%	2356
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 4 8% 49%	2090
	21st to end	Day	10% 6% 1 5% 4 3 4 4 5% 7% 50%	2090
October	1st to 10th	Day	7% 7% 2 6% 4 4 4 4 7% 8% 46%	3250
	11th to 20th	Day	5% 7% 2 6% 3 4 4 3 6% 8% 52%	3092
	21st to end	Day	8% 6% 2 5% 4 4 4 5% 7% 6% 50%	3101
November	1st to 10th	Day	12% 13% 3 7% 5% 5% 4 4 5% 7% 35%	1597
	11th to 20th	Day	6% 9% 3 8% 6% 5% 5% 4 6% 7% 40%	1600
	21st to end	Day	5% 11% 4 11% 5% 5% 4 4 7% 10% 34%	1480
December	1st to 10th	Day	6% 14% 4 8% 8% 5% 5% 3 5% 6% 36%	2290
	11th to 20th	Day	4 11% 4 9% 7% 7% 6% 5% 6% 7% 35%	2642
	21st to end	Day	4 9% 4 8% 6% 4 5% 4 5% 7% 43%	3498
January	1st to 10th	Night	5% 16% 5% 11% 6% 5% 4 4 5% 9% 30%	6766
	11th to 20th	Night	4 12% 5% 10% 5% 5% 6% 4 6% 7% 36%	6739
	21st to end	Night	3 10% 5% 9% 5% 5% 5% 4 5% 7% 43%	6980
February	1st to 10th	Night	7% 13% 4 11% 6% 5% 5% 4 6% 7% 32%	2681
	11th to 20th	Night	6% 13% 4 12% 6% 5% 6% 4 6% 8% 30%	2532
	21st to end	Night	5% 13% 5% 10% 6% 5% 5% 4 5% 8% 34%	2038
March	1st to 10th	Night	4 9% 5% 11% 7% 5% 5% 4 6% 7% 36%	3654
	11th to 20th	Night	7% 7% 3 6% 5% 5% 5% 4 7% 8% 44%	3490
	21st to end	Night	13% 18% 5% 10% 5% 5% 4 4 6% 7% 23%	3828
April	1st to 10th	Night	9% 12% 4 8% 5% 5% 5% 5% 6% 7% 35%	1862
	11th to 20th	Night	10% 10% 3 9% 6% 4 5% 4 7% 8% 34%	1691
	21st to end	Night	10% 10% 3 7% 5% 5% 6% 4 7% 7% 35%	1710
May	1st to 10th	Night	19% 12% 3 7% 5% 5% 5% 4 5% 6% 30%	2732
	11th to 20th	Night	9% 6% 3 7% 5% 6% 5% 4 7% 9% 39%	2296
	21st to end	Night	15% 8% 3 9% 7% 6% 6% 5% 6% 8% 27%	2414
June	1st to 10th	Night	14% 7% 3 8% 4 4 4 4 6% 8% 38%	1330
	11th to 20th	Night	14% 6% 2 6% 5% 6% 4 5% 7% 8% 36%	1330
	21st to end	Night	6% 3 1 5% 4 4 5% 5% 7% 9% 51%	1330
July	1st to 10th	Night	3 2 1 4 4 5% 6% 4 7% 9% 55%	2220
	11th to 20th	Night	5% 4 1 3 3 3 4 3 5% 10% 58%	2220
	21st to end	Night	3 2 1 4 3 3 3 4 5% 8% 64%	2469
August	1st to 10th	Night	8% 4 2 5% 4 4 4 4 5% 8% 53%	2683
	11th to 20th	Night	4 3 1 5% 4 5% 6% 5% 8% 11% 47%	2811
	21st to end	Night	8% 4 1 4 3 3 3 3 5% 7% 59%	3146
September	1st to 10th	Night	10% 5% 2 5% 3 4 3 4 5% 7% 53%	1822
	11th to 20th	Night	12% 6% 1 5% 4 4 3 3 6% 7% 50%	2090
	21st to end	Night	7% 7% 2 6% 3 4 4 4 6% 7% 51%	2090
October	1st to 10th	Night	7% 5% 2 5% 4 4 4 3 6% 7% 54%	3721
	11th to 20th	Night	6% 7% 2 6% 4 4 4 4 6% 9% 49%	3833
	21st to end	Night	5% 6% 3 7% 5% 5% 6% 4 6% 8% 46%	4457
November	1st to 10th	Night	11% 12% 3 7% 5% 5% 4 4 5% 7% 36%	2682
	11th to 20th	Night	5% 10% 3 8% 5% 5% 5% 4 7% 7% 41%	2800
	21st to end	Night	5% 12% 4 9% 5% 5% 3 4 6% 8% 39%	2918
December	1st to 10th	Night	4 12% 4 9% 7% 6% 7% 5% 6% 7% 33%	4890
	11th to 20th	Night	4 11% 5% 11% 6% 6% 6% 5% 7% 9% 32%	5550
	21st to end	Night	4 9% 4 8% 4 4 5% 4 5% 8% 44%	7458

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	55% 6% 12% 22% 4 1	3179
	11th to 20th	Day	50% 6% 13% 15% 15% 1	3196
	21st to end	Day	38% 5% 15% 33% 8% 1	4004
February	1st to 10th	Day	54% 5% 14% 17% 9% 1	1718
	11th to 20th	Day	52% 7% 14% 19% 8% 1	1764
	21st to end	Day	49% 6% 14% 20% 10% 2	1506
March	1st to 10th	Day	40% 8% 13% 27% 11%	3220
	11th to 20th	Day	34% 7% 23% 26% 10% 1	3490
	21st to end	Day	55% 9% 14% 17% 5%	3825
April	1st to 10th	Day	48% 7% 12% 23% 8% 1	2316
	11th to 20th	Day	49% 5% 10% 25% 9% 2	2440
	21st to end	Day	45% 6% 14% 24% 10% 1	2470
May	1st to 10th	Day	53% 4 10% 25% 6%	4238
	11th to 20th	Day	36% 7% 16% 31% 10% 1	4600
	21st to end	Day	43% 8% 14% 24% 9% 1	5162
June	1st to 10th	Day	40% 6% 18% 22% 12% 2	2850
	11th to 20th	Day	44% 6% 14% 22% 12% 2	2850
	21st to end	Day	27% 6% 17% 33% 13% 3	2850
July	1st to 10th	Day	23% 5% 15% 30% 21% 6%	4666
	11th to 20th	Day	19% 4 15% 34% 21% 7%	4659
	21st to end	Day	13% 3 9% 30% 27% 18%	4919
August	1st to 10th	Day	27% 5% 12% 35% 19% 2	4233
	11th to 20th	Day	25% 5% 16% 39% 13% 2	4067
	21st to end	Day	23% 4 12% 41% 18% 3	4520
September	1st to 10th	Day	28% 3 13% 28% 19% 9%	2356
	11th to 20th	Day	35% 4 13% 30% 14% 4	2090
	21st to end	Day	32% 5% 13% 31% 15% 3	2090
October	1st to 10th	Day	34% 5% 12% 33% 14% 2	3250
	11th to 20th	Day	30% 5% 17% 32% 16% 1	3092
	21st to end	Day	33% 5% 11% 37% 13% 2	3101
November	1st to 10th	Day	49% 6% 13% 23% 8% 2	1597
	11th to 20th	Day	43% 5% 19% 24% 9% 1	1600
	21st to end	Day	45% 6% 18% 21% 8% 2	1480
December	1st to 10th	Day	49% 5% 15% 24% 5% 2	2290
	11th to 20th	Day	47% 6% 20% 23% 4 1	2644
	21st to end	Day	40% 5% 14% 24% 16% 1	3498
January	1st to 10th	Night	51% 6% 17% 21% 5% 1	6766
	11th to 20th	Night	47% 5% 15% 18% 14% 1	6780
	21st to end	Night	41% 5% 15% 29% 10% 1	6980
February	1st to 10th	Night	51% 5% 13% 18% 12% 1	2681
	11th to 20th	Night	51% 6% 15% 18% 9% 1	2533
	21st to end	Night	48% 5% 16% 20% 9% 2	2038
March	1st to 10th	Night	45% 7% 14% 25% 9%	3654
	11th to 20th	Night	35% 7% 21% 26% 11% 1	3490
	21st to end	Night	59% 7% 14% 15% 3 1	3828
April	1st to 10th	Night	45% 7% 15% 23% 10%	1862
	11th to 20th	Night	44% 7% 12% 24% 13% 1	1691
	21st to end	Night	45% 6% 14% 25% 9% 1	1710
May	1st to 10th	Night	54% 5% 11% 23% 7% 1	2732
	11th to 20th	Night	35% 9% 15% 29% 12% 1	2296
	21st to end	Night	49% 11% 13% 20% 6% 1	2414
June	1st to 10th	Night	42% 7% 13% 26% 11% 2	1330
	11th to 20th	Night	42% 6% 15% 23% 11% 2	1330
	21st to end	Night	27% 5% 16% 32% 15% 4	1330
July	1st to 10th	Night	21% 7% 18% 27% 22% 4	2185
	11th to 20th	Night	22% 5% 13% 32% 19% 9%	2178
	21st to end	Night	18% 3 8% 28% 27% 16%	2391
August	1st to 10th	Night	30% 5% 11% 31% 18% 6%	2675
	11th to 20th	Night	28% 7% 17% 27% 17% 3	2838
	21st to end	Night	25% 4 11% 36% 20% 4	3146
September	1st to 10th	Night	30% 5% 10% 27% 20% 8%	1822
	11th to 20th	Night	32% 5% 12% 28% 16% 6%	2090
	21st to end	Night	32% 4 12% 32% 17% 3	2090
October	1st to 10th	Night	29% 4 11% 34% 19% 3	3721
	11th to 20th	Night	31% 4 15% 31% 16% 3	3833
	21st to end	Night	36% 5% 11% 34% 14% 1	4457
November	1st to 10th	Night	47% 6% 14% 22% 9% 2	2682
	11th to 20th	Night	40% 6% 19% 23% 12%	2800
	21st to end	Night	43% 5% 21% 20% 10% 1	2918
December	1st to 10th	Night	49% 6% 17% 19% 8% 1	4890
	11th to 20th	Night	47% 7% 24% 18% 4 1	5547
	21st to end	Night	38% 4 12% 26% 17% 2	7458

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	14% 13% 34% 20% 12% 8%	200
	11th to 20th	Day	11% 13% 35% 28% 13% 2	200
	21st to end	Day	10% 17% 37% 25% 7% 3	220
February	1st to 10th	Day	20% 12% 31% 25% 9% 3	260
	11th to 20th	Day	12% 13% 37% 27% 9% 2	300
	21st to end	Day	13% 16% 29% 29% 12% 1	294
March	1st to 10th	Day	12% 16% 35% 23% 12% 3	460
	11th to 20th	Day	11% 13% 30% 27% 14% 5%	460
	21st to end	Day	14% 12% 34% 24% 12% 3	506
April	1st to 10th	Day	15% 18% 31% 25% 10% 1	460
	11th to 20th	Day	14% 13% 29% 29% 13% 1	452
	21st to end	Day	17% 12% 25% 29% 14% 3	460
May	1st to 10th	Day	15% 8% 27% 22% 21% 7%	539
	11th to 20th	Day	16% 6% 21% 30% 21% 6%	675
	21st to end	Day	19% 6% 19% 24% 24% 7%	734
June	1st to 10th	Day	14% 9% 24% 29% 19% 5%	680
	11th to 20th	Day	17% 11% 28% 26% 15% 2	680
	21st to end	Day	9% 6% 22% 33% 24% 7%	680
July	1st to 10th	Day	7% 2 21% 34% 28% 8%	671
	11th to 20th	Day	7% 4 25% 37% 22% 5%	668
	21st to end	Day	4 6% 20% 37% 25% 9%	705
August	1st to 10th	Day	7% 3 20% 32% 28% 9%	487
	11th to 20th	Day	6% 3 20% 30% 30% 11%	477
	21st to end	Day	10% 7% 24% 24% 27% 9%	539
September	1st to 10th	Day	11% 9% 26% 27% 22% 4	490
	11th to 20th	Day	13% 10% 26% 29% 17% 6%	490
	21st to end	Day	14% 11% 31% 27% 11% 5%	490
October	1st to 10th	Day	15% 9% 24% 29% 18% 5%	354
	11th to 20th	Day	12% 14% 31% 25% 14% 4	300
	21st to end	Day	19% 15% 33% 21% 10% 2	330
November	1st to 10th	Day	24% 13% 31% 21% 10% 2	300
	11th to 20th	Day	13% 18% 40% 22% 6% 1	300
	21st to end	Day	10% 18% 35% 22% 10% 5%	240
December	1st to 10th	Day	14% 18% 37% 21% 10% 1	200
	11th to 20th	Day	15% 18% 38% 20% 9% 1	200
	21st to end	Day	18% 11% 31% 25% 10% 4	220
January	1st to 10th	Night	12% 16% 39% 24% 9% 1	1000
	11th to 20th	Night	12% 16% 36% 27% 8% 1	1000
	21st to end	Night	13% 17% 40% 22% 7% 2	895
February	1st to 10th	Night	16% 11% 33% 28% 11% 2	800
	11th to 20th	Night	11% 11% 38% 29% 10% 1	784
	21st to end	Night	12% 11% 30% 29% 15% 2	646
March	1st to 10th	Night	9% 12% 35% 31% 12% 2	760
	11th to 20th	Night	11% 12% 35% 29% 10% 2	760
	21st to end	Night	14% 12% 33% 29% 11% 1	836
April	1st to 10th	Night	14% 11% 38% 25% 11% 1	656
	11th to 20th	Night	18% 6% 35% 32% 9%	563
	21st to end	Night	15% 9% 32% 34% 10% 1	570
May	1st to 10th	Night	13% 8% 28% 32% 18% 1	570
	11th to 20th	Night	12% 5% 27% 38% 17% 1	432
	21st to end	Night	22% 7% 21% 30% 18% 1	411
June	1st to 10th	Night	16% 10% 28% 30% 16% 1	380
	11th to 20th	Night	16% 9% 33% 27% 14%	380
	21st to end	Night	7% 5% 29% 41% 15% 2	380
July	1st to 10th	Night	6% 4 21% 48% 21%	370
	11th to 20th	Night	9% 3 27% 43% 18%	368
	21st to end	Night	4 4 22% 46% 23% 2	416
August	1st to 10th	Night	8% 2 21% 46% 21% 2	467
	11th to 20th	Night	8% 3 22% 43% 23% 1	564
	21st to end	Night	8% 5% 27% 40% 20% 1	627
September	1st to 10th	Night	11% 6% 27% 41% 14% 2	592
	11th to 20th	Night	14% 5% 25% 36% 19% 1	760
	21st to end	Night	10% 9% 32% 34% 13% 2	760
October	1st to 10th	Night	15% 7% 28% 34% 15% 1	760
	11th to 20th	Night	14% 9% 36% 29% 11% 2	760
	21st to end	Night	11% 16% 38% 27% 9%	836
November	1st to 10th	Night	17% 13% 40% 24% 6%	927
	11th to 20th	Night	12% 17% 43% 22% 6% 1	1000
	21st to end	Night	10% 13% 42% 27% 7% 1	1000
December	1st to 10th	Night	13% 12% 36% 27% 9% 2	1000
	11th to 20th	Night	9% 15% 41% 26% 8% 1	1000
	21st to end	Night	13% 14% 38% 26% 8% 2	1100

Page generated at 2025-02-22 04:51:35. Version ac07

Copyright © 2025 Attilla Danko.