Claresholm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Claresholm 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	7% 8% 3 7% 5% 5% 5% 4 6% 8% 42%	112123
	Night	6% 9% 3 8% 5% 5% 5% 4 6% 8% 41%	115219
Transparency	Day	36% 8% 16% 25% 12% 3	111870
	Night	38% 9% 15% 23% 12% 2	115118
Seeing	Day	12% 14% 27% 27% 15% 4	15621
	Night	11% 12% 31% 31% 13% 2	24975

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	2 12% 7% 15% 6% 4 4 3 5% 8% 34%	3179
	11th to 20th	Day	3 9% 4 9% 7% 7% 5% 5% 7% 7% 38%	3315
	21st to end	Day	2 6% 4 9% 5% 5% 5% 4 6% 10% 44%	4004
February	1st to 10th	Day	4 10% 5% 11% 7% 8% 6% 4 7% 8% 31%	1640
	11th to 20th	Day	3 12% 5% 9% 6% 6% 6% 5% 8% 9% 31%	1755
	21st to end	Day	4 12% 6% 10% 8% 5% 4 5% 6% 7% 34%	1571
March	1st to 10th	Day	2 9% 3 10% 7% 7% 6% 5% 6% 8% 37%	3138
	11th to 20th	Day	6% 9% 2 6% 4 4 4 4 5% 8% 49%	3480
	21st to end	Day	10% 16% 6% 11% 5% 5% 5% 4 5% 7% 26%	3841
April	1st to 10th	Day	8% 14% 4 9% 7% 6% 5% 4 6% 8% 30%	2333
	11th to 20th	Day	11% 13% 4 8% 5% 4 5% 4 7% 8% 31%	2440
	21st to end	Day	11% 11% 3 7% 6% 5% 5% 4 6% 8% 34%	2470
May	1st to 10th	Day	18% 15% 4 7% 4 4 4 3 5% 6% 30%	4187
	11th to 20th	Day	10% 7% 3 7% 6% 6% 6% 5% 8% 8% 33%	4694
	21st to end	Day	16% 9% 3 8% 6% 5% 6% 5% 7% 8% 28%	5161
June	1st to 10th	Day	14% 8% 2 7% 5% 6% 6% 4 7% 8% 33%	2850
	11th to 20th	Day	17% 8% 2 7% 6% 5% 6% 5% 7% 7% 30%	2850
	21st to end	Day	8% 4 1 5% 4 4 6% 5% 7% 8% 47%	2850
July	1st to 10th	Day	6% 4 1 5% 4 4 4 4 6% 8% 53%	4740
	11th to 20th	Day	4 2 1 3 3 3 4 4 8% 10% 56%	4740
	21st to end	Day	2 2 1 3 3 3 3 4 6% 8% 64%	4959
August	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 7% 10% 47%	4371
	11th to 20th	Day	6% 3 2 4 4 4 5% 4 6% 9% 52%	4028
	21st to end	Day	8% 3 1 4 3 3 4 4 7% 8% 57%	4521
September	1st to 10th	Day	11% 5% 2 5% 3 3 4 2 5% 6% 54%	2337
	11th to 20th	Day	13% 5% 2 5% 3 4 4 3 5% 8% 48%	2090
	21st to end	Day	10% 6% 2 4 4 4 3 4 6% 8% 49%	2090
October	1st to 10th	Day	7% 7% 2 6% 4 4 4 5% 8% 9% 44%	3340
	11th to 20th	Day	5% 7% 2 5% 3 3 4 4 7% 11% 49%	2971
	21st to end	Day	6% 8% 2 6% 4 4 5% 6% 6% 8% 45%	3101
November	1st to 10th	Day	10% 11% 5% 9% 5% 4 4 4 6% 8% 36%	1654
	11th to 20th	Day	4 10% 3 9% 5% 5% 5% 3 6% 8% 42%	1593
	21st to end	Day	4 10% 5% 9% 4 3 4 5% 7% 11% 37%	1400
December	1st to 10th	Day	1 9% 4 10% 6% 5% 5% 4 7% 9% 40%	2290
	11th to 20th	Day	3 8% 4 11% 6% 6% 6% 5% 7% 9% 35%	2642
	21st to end	Day	3 9% 5% 11% 5% 4 4 4 5% 8% 42%	3498
January	1st to 10th	Night	3 15% 6% 12% 6% 6% 6% 4 5% 7% 29%	6766
	11th to 20th	Night	2 9% 4 12% 7% 6% 6% 5% 7% 8% 35%	6629
	21st to end	Night	2 8% 5% 10% 5% 5% 6% 5% 6% 8% 41%	6952
February	1st to 10th	Night	4 10% 4 12% 7% 6% 5% 4 6% 7% 33%	2760
	11th to 20th	Night	4 13% 5% 11% 6% 5% 6% 5% 6% 8% 31%	2532
	21st to end	Night	3 11% 5% 10% 8% 5% 5% 4 5% 6% 36%	1975
March	1st to 10th	Night	2 8% 5% 13% 8% 6% 5% 4 6% 8% 35%	3736
	11th to 20th	Night	4 8% 2 6% 5% 4 4 4 6% 9% 47%	3498
	21st to end	Night	11% 18% 6% 11% 5% 4 4 4 5% 7% 24%	3809
April	1st to 10th	Night	8% 13% 4 8% 5% 4 4 4 6% 7% 37%	1846
	11th to 20th	Night	9% 11% 4 10% 5% 5% 5% 4 8% 6% 33%	1691
	21st to end	Night	10% 10% 3 9% 6% 4 5% 5% 5% 5% 38%	1710
May	1st to 10th	Night	16% 14% 4 8% 5% 4 4 3 4 6% 31%	2776
	11th to 20th	Night	9% 7% 2 7% 4 5% 5% 4 7% 9% 40%	2199
	21st to end	Night	14% 7% 2 8% 6% 6% 6% 4 7% 8% 32%	2414
June	1st to 10th	Night	13% 7% 2 5% 5% 5% 5% 5% 6% 7% 40%	1330
	11th to 20th	Night	18% 6% 2 6% 5% 5% 4 4 6% 8% 35%	1330
	21st to end	Night	7% 4 2 4 3 5% 5% 5% 7% 7% 51%	1330
July	1st to 10th	Night	3 3 2 5% 3 5% 5% 5% 7% 10% 52%	2220
	11th to 20th	Night	4 3 1 4 4 4 5% 4 6% 8% 57%	2220
	21st to end	Night	3 3 2 4 3 3 2 3 5% 5% 68%	2589
August	1st to 10th	Night	8% 4 2 5% 4 5% 5% 4 6% 8% 49%	2560
	11th to 20th	Night	4 4 2 6% 5% 4 6% 5% 7% 10% 47%	2811
	21st to end	Night	6% 3 1 4 3 4 4 3 6% 8% 59%	3146
September	1st to 10th	Night	9% 3 1 5% 3 4 4 3 5% 7% 56%	1839
	11th to 20th	Night	11% 6% 2 4 3 2 3 3 4 7% 54%	2090
	21st to end	Night	10% 6% 2 4 3 3 4 3 6% 7% 52%	2090
October	1st to 10th	Night	6% 5% 2 5% 3 3 4 4 5% 7% 57%	3635
	11th to 20th	Night	5% 5% 2 5% 3 4 5% 4 6% 9% 52%	3952
	21st to end	Night	5% 7% 2 7% 4 4 5% 4 6% 8% 48%	4457
November	1st to 10th	Night	8% 13% 3 7% 5% 4 4 5% 6% 7% 38%	2624
	11th to 20th	Night	3 9% 3 7% 5% 5% 5% 5% 7% 9% 42%	2805
	21st to end	Night	4 11% 4 7% 5% 4 4 4 7% 10% 40%	3000
December	1st to 10th	Night	3 8% 3 8% 6% 5% 6% 5% 8% 10% 39%	4890
	11th to 20th	Night	3 9% 5% 9% 6% 6% 6% 5% 8% 9% 33%	5550
	21st to end	Night	4 10% 5% 9% 5% 4 5% 5% 6% 8% 40%	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	48% 9% 12% 21% 9% 2	3179
	11th to 20th	Day	43% 8% 12% 19% 16% 2	3336
	21st to end	Day	31% 10% 14% 32% 12% 1	4004
February	1st to 10th	Day	49% 9% 15% 16% 9% 2	1640
	11th to 20th	Day	46% 9% 16% 19% 8% 2	1764
	21st to end	Day	48% 8% 13% 18% 12% 1	1571
March	1st to 10th	Day	37% 12% 18% 21% 13% 1	3138
	11th to 20th	Day	31% 10% 20% 27% 12% 1	3481
	21st to end	Day	53% 10% 16% 17% 4	3841
April	1st to 10th	Day	49% 9% 15% 20% 7% 1	2333
	11th to 20th	Day	47% 8% 15% 19% 9% 2	2440
	21st to end	Day	45% 8% 15% 20% 10% 1	2470
May	1st to 10th	Day	53% 7% 12% 23% 5%	4187
	11th to 20th	Day	39% 12% 18% 22% 9% 1	4698
	21st to end	Day	46% 12% 19% 15% 7% 1	5162
June	1st to 10th	Day	44% 9% 17% 19% 10% 2	2850
	11th to 20th	Day	48% 9% 14% 17% 9% 2	2850
	21st to end	Day	30% 9% 19% 27% 12% 3	2850
July	1st to 10th	Day	26% 8% 13% 30% 17% 6%	4666
	11th to 20th	Day	19% 8% 17% 35% 17% 4	4659
	21st to end	Day	17% 6% 11% 26% 25% 16%	4802
August	1st to 10th	Day	30% 8% 17% 29% 14% 3	4354
	11th to 20th	Day	26% 8% 21% 33% 10% 2	4067
	21st to end	Day	24% 5% 13% 39% 16% 2	4520
September	1st to 10th	Day	30% 6% 14% 24% 18% 8%	2337
	11th to 20th	Day	34% 8% 14% 27% 14% 3	2090
	21st to end	Day	32% 7% 14% 30% 14% 3	2090
October	1st to 10th	Day	32% 8% 13% 33% 12% 1	3340
	11th to 20th	Day	28% 6% 22% 25% 16% 2	2971
	21st to end	Day	33% 9% 12% 29% 12% 4	3101
November	1st to 10th	Day	46% 8% 13% 22% 11%	1654
	11th to 20th	Day	39% 8% 20% 21% 11% 1	1593
	21st to end	Day	39% 9% 19% 20% 10% 2	1400
December	1st to 10th	Day	41% 8% 16% 26% 8% 2	2290
	11th to 20th	Day	44% 9% 20% 20% 6% 1	2644
	21st to end	Day	39% 7% 12% 22% 18% 1	3498
January	1st to 10th	Night	53% 8% 12% 19% 6% 2	6766
	11th to 20th	Night	45% 8% 13% 18% 14% 2	6670
	21st to end	Night	37% 9% 15% 25% 13% 1	6952
February	1st to 10th	Night	47% 9% 13% 16% 12% 2	2760
	11th to 20th	Night	49% 9% 13% 20% 9% 1	2533
	21st to end	Night	47% 7% 13% 20% 10% 2	1975
March	1st to 10th	Night	42% 12% 15% 22% 10%	3736
	11th to 20th	Night	30% 12% 22% 23% 13%	3498
	21st to end	Night	58% 9% 14% 15% 4	3809
April	1st to 10th	Night	44% 9% 14% 21% 11% 1	1846
	11th to 20th	Night	46% 10% 13% 21% 9% 1	1691
	21st to end	Night	44% 9% 14% 22% 9% 2	1710
May	1st to 10th	Night	53% 7% 13% 22% 5%	2776
	11th to 20th	Night	33% 13% 16% 29% 8% 1	2199
	21st to end	Night	43% 15% 17% 16% 7% 1	2414
June	1st to 10th	Night	41% 8% 18% 22% 11% 1	1330
	11th to 20th	Night	44% 8% 16% 20% 10% 1	1330
	21st to end	Night	27% 10% 19% 26% 16% 2	1330
July	1st to 10th	Night	26% 8% 20% 23% 18% 5%	2185
	11th to 20th	Night	23% 8% 16% 30% 16% 7%	2178
	21st to end	Night	19% 4 9% 29% 23% 16%	2507
August	1st to 10th	Night	30% 9% 16% 25% 17% 3	2552
	11th to 20th	Night	30% 9% 17% 28% 14% 2	2838
	21st to end	Night	22% 6% 14% 37% 18% 4	3146
September	1st to 10th	Night	28% 6% 16% 28% 17% 6%	1839
	11th to 20th	Night	31% 6% 14% 27% 17% 5%	2090
	21st to end	Night	30% 7% 15% 28% 15% 4	2090
October	1st to 10th	Night	26% 6% 11% 31% 23% 3	3635
	11th to 20th	Night	29% 6% 18% 26% 18% 3	3952
	21st to end	Night	33% 6% 14% 31% 16% 1	4457
November	1st to 10th	Night	43% 8% 15% 21% 11% 1	2624
	11th to 20th	Night	36% 10% 18% 20% 15% 1	2805
	21st to end	Night	38% 8% 20% 20% 11% 3	3000
December	1st to 10th	Night	40% 10% 20% 19% 10% 2	4890
	11th to 20th	Night	43% 11% 22% 18% 6%	5547
	21st to end	Night	39% 8% 14% 23% 13% 3	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	7% 15% 30% 31% 11% 8%	200
	11th to 20th	Day	11% 16% 30% 26% 14% 5%	200
	21st to end	Day	7% 22% 36% 24% 9% 2	220
February	1st to 10th	Day	11% 22% 32% 23% 9% 3	220
	11th to 20th	Day	10% 15% 30% 32% 11% 3	300
	21st to end	Day	11% 21% 31% 26% 10% 1	359
March	1st to 10th	Day	9% 24% 34% 21% 8% 4	460
	11th to 20th	Day	10% 18% 28% 28% 12% 3	460
	21st to end	Day	12% 19% 35% 21% 10% 3	506
April	1st to 10th	Day	13% 22% 32% 22% 9%	460
	11th to 20th	Day	16% 15% 29% 21% 15% 3	452
	21st to end	Day	16% 20% 29% 23% 10% 3	460
May	1st to 10th	Day	18% 10% 25% 28% 14% 5%	478
	11th to 20th	Day	17% 8% 21% 28% 20% 5%	675
	21st to end	Day	19% 10% 17% 28% 20% 6%	734
June	1st to 10th	Day	14% 15% 25% 28% 15% 3	680
	11th to 20th	Day	19% 13% 24% 27% 13% 3	680
	21st to end	Day	9% 7% 25% 30% 21% 6%	680
July	1st to 10th	Day	8% 5% 23% 33% 24% 6%	671
	11th to 20th	Day	6% 8% 23% 34% 23% 6%	668
	21st to end	Day	4 8% 26% 36% 20% 6%	635
August	1st to 10th	Day	10% 8% 21% 33% 22% 6%	487
	11th to 20th	Day	6% 7% 25% 30% 24% 8%	477
	21st to end	Day	9% 11% 27% 28% 18% 7%	539
September	1st to 10th	Day	12% 11% 28% 27% 16% 6%	490
	11th to 20th	Day	14% 11% 26% 28% 15% 5%	490
	21st to end	Day	16% 19% 27% 25% 10% 3	490
October	1st to 10th	Day	16% 11% 23% 26% 19% 5%	405
	11th to 20th	Day	12% 19% 27% 21% 15% 7%	300
	21st to end	Day	16% 20% 25% 26% 11% 3	330
November	1st to 10th	Day	19% 20% 29% 20% 10% 2	300
	11th to 20th	Day	13% 21% 32% 25% 9% 1	295
	21st to end	Day	8% 23% 28% 25% 9% 8%	200
December	1st to 10th	Day	10% 19% 28% 27% 13% 5%	200
	11th to 20th	Day	10% 19% 37% 22% 9% 4	200
	21st to end	Day	12% 13% 30% 28% 13% 5%	220
January	1st to 10th	Night	11% 21% 31% 27% 9% 1	1000
	11th to 20th	Night	10% 15% 34% 31% 9% 1	955
	21st to end	Night	9% 14% 36% 30% 9% 1	880
February	1st to 10th	Night	9% 17% 32% 28% 13% 3	800
	11th to 20th	Night	9% 10% 36% 33% 10% 2	784
	21st to end	Night	10% 11% 32% 29% 16% 2	646
March	1st to 10th	Night	8% 14% 35% 31% 11% 2	760
	11th to 20th	Night	9% 14% 34% 31% 9% 2	760
	21st to end	Night	12% 12% 31% 31% 11% 3	836
April	1st to 10th	Night	13% 13% 35% 28% 10% 1	706
	11th to 20th	Night	16% 9% 35% 29% 10% 1	563
	21st to end	Night	14% 11% 31% 33% 10% 1	570
May	1st to 10th	Night	14% 10% 27% 32% 15%	542
	11th to 20th	Night	13% 6% 23% 36% 22% 1	374
	21st to end	Night	19% 6% 23% 31% 20% 1	411
June	1st to 10th	Night	14% 9% 27% 33% 14% 2	380
	11th to 20th	Night	20% 8% 29% 29% 14%	380
	21st to end	Night	7% 5% 25% 41% 21% 1	380
July	1st to 10th	Night	8% 4 19% 42% 27% 1	370
	11th to 20th	Night	7% 2 24% 45% 21% 1	368
	21st to end	Night	4 3 24% 43% 24% 1	416
August	1st to 10th	Night	9% 2 17% 42% 28% 2	396
	11th to 20th	Night	8% 2 20% 43% 26% 2	564
	21st to end	Night	8% 6% 25% 42% 18% 1	627
September	1st to 10th	Night	10% 5% 25% 35% 23% 2	662
	11th to 20th	Night	14% 5% 25% 33% 21% 2	760
	21st to end	Night	12% 8% 33% 30% 13% 3	760
October	1st to 10th	Night	14% 9% 26% 32% 17% 2	760
	11th to 20th	Night	12% 11% 32% 29% 14% 2	760
	21st to end	Night	12% 14% 35% 28% 10% 1	836
November	1st to 10th	Night	17% 14% 38% 22% 8%	869
	11th to 20th	Night	11% 20% 39% 23% 5% 2	1000
	21st to end	Night	10% 17% 38% 25% 8% 2	1000
December	1st to 10th	Night	10% 13% 35% 30% 11% 2	1000
	11th to 20th	Night	8% 16% 38% 29% 8% 1	1000
	21st to end	Night	11% 16% 34% 28% 10% 2	1100

Page generated at 2025-02-22 04:51:39. Version ac07

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