Assiniboia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Assiniboia clear sky chart from 2005-11-06 to 2025-05-11.

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 8% 5% 5% 5% 4 6% 7% 40%	117169
	Night	7% 9% 3 9% 6% 5% 5% 4 6% 7% 39%	120529
Transparency	Day	41% 6% 16% 25% 11% 1	116903
	Night	43% 5% 15% 25% 11% 1	120384
Seeing	Day	13% 9% 30% 29% 15% 4	16543
	Night	12% 8% 33% 34% 12% 1	26156

By Month

Percentage Cloud Cover SW (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	5% 15% 5% 13% 8% 7% 7% 5% 5% 5% 24%	3179
	11th to 20th	Day	3 8% 4 11% 7% 7% 11% 8% 7% 7% 27%	3478
	21st to end	Day	5% 9% 4 11% 6% 4 5% 3 5% 7% 40%	4004
February	1st to 10th	Day	9% 14% 6% 12% 8% 6% 7% 3 6% 7% 24%	1734
	11th to 20th	Day	6% 13% 4 11% 7% 8% 6% 5% 7% 6% 27%	1755
	21st to end	Day	4 12% 4 12% 7% 6% 6% 6% 7% 7% 29%	1575
March	1st to 10th	Day	5% 12% 6% 15% 6% 5% 3 3 5% 7% 33%	4500
	11th to 20th	Day	5% 11% 5% 12% 6% 5% 5% 4 7% 9% 32%	4908
	21st to end	Day	7% 15% 6% 15% 5% 5% 5% 4 6% 7% 24%	5790
April	1st to 10th	Day	8% 10% 3 8% 6% 5% 5% 4 6% 8% 37%	2400
	11th to 20th	Day	12% 13% 5% 9% 6% 5% 5% 4 6% 8% 27%	2376
	21st to end	Day	16% 9% 3 6% 4 4 5% 4 4 7% 37%	2755
May	1st to 10th	Day	18% 11% 4 7% 4 4 4 4 5% 6% 33%	4570
	11th to 20th	Day	9% 7% 3 8% 5% 5% 6% 5% 7% 9% 36%	4390
	21st to end	Day	15% 7% 3 8% 5% 5% 5% 4 6% 7% 34%	4825
June	1st to 10th	Day	16% 6% 2 5% 5% 4 4 5% 6% 7% 39%	2783
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 4 6% 7% 34%	2850
	21st to end	Day	9% 5% 2 5% 5% 5% 5% 5% 7% 9% 45%	2850
July	1st to 10th	Day	4 4 2 6% 5% 6% 6% 5% 8% 9% 46%	4740
	11th to 20th	Day	4 2 1 4 3 3 4 4 7% 9% 59%	4633
	21st to end	Day	4 2 1 4 3 3 4 4 5% 7% 64%	4802
August	1st to 10th	Day	8% 4 2 5% 4 5% 4 4 5% 6% 54%	4411
	11th to 20th	Day	6% 3 1 4 4 4 4 4 6% 9% 55%	4190
	21st to end	Day	9% 4 2 4 3 3 3 2 5% 7% 58%	4309
September	1st to 10th	Day	11% 5% 2 5% 4 3 3 4 5% 7% 50%	2280
	11th to 20th	Day	12% 7% 2 6% 4 3 4 3 5% 7% 46%	2280
	21st to end	Day	13% 5% 2 5% 3 4 3 3 6% 7% 48%	2033
October	1st to 10th	Day	9% 5% 2 5% 3 4 4 3 5% 7% 53%	3170
	11th to 20th	Day	7% 5% 3 5% 4 3 3 3 6% 10% 51%	3121
	21st to end	Day	6% 9% 2 7% 4 5% 5% 5% 6% 8% 44%	3091
November	1st to 10th	Day	11% 13% 4 8% 6% 4 3 4 5% 7% 35%	1613
	11th to 20th	Day	6% 12% 5% 13% 6% 5% 4 4 6% 6% 35%	1600
	21st to end	Day	9% 11% 5% 8% 6% 7% 5% 5% 6% 6% 32%	1600
December	1st to 10th	Day	4 10% 4 14% 8% 7% 6% 4 6% 7% 29%	2457
	11th to 20th	Day	7% 14% 6% 14% 7% 5% 6% 5% 6% 6% 23%	2619
	21st to end	Day	6% 7% 3 8% 7% 4 5% 3 5% 8% 43%	3498
January	1st to 10th	Night	3 10% 5% 14% 8% 7% 7% 5% 6% 6% 29%	6766
	11th to 20th	Night	3 8% 4 13% 9% 9% 8% 6% 10% 7% 25%	6492
	21st to end	Night	3 10% 5% 12% 6% 4 5% 4 6% 8% 37%	6974
February	1st to 10th	Night	7% 13% 5% 10% 8% 7% 6% 5% 7% 7% 27%	2685
	11th to 20th	Night	6% 12% 4 11% 7% 5% 5% 4 7% 7% 32%	2532
	21st to end	Night	5% 9% 4 10% 6% 6% 6% 4 6% 7% 36%	2055
March	1st to 10th	Night	5% 8% 3 12% 7% 6% 5% 4 6% 9% 34%	5374
	11th to 20th	Night	6% 10% 4 10% 5% 5% 5% 5% 6% 8% 37%	5073
	21st to end	Night	8% 13% 7% 16% 7% 5% 6% 4 5% 6% 22%	5170
April	1st to 10th	Night	6% 10% 3 8% 5% 4 4 4 8% 9% 39%	2000
	11th to 20th	Night	12% 12% 4 9% 4 4 5% 4 6% 8% 33%	1969
	21st to end	Night	11% 8% 3 8% 5% 4 5% 5% 7% 7% 37%	1645
May	1st to 10th	Night	19% 10% 3 7% 4 4 3 3 6% 7% 34%	2620
	11th to 20th	Night	11% 6% 2 6% 4 5% 5% 4 7% 10% 41%	2521
	21st to end	Night	15% 6% 2 6% 5% 5% 5% 5% 7% 9% 37%	2762
June	1st to 10th	Night	12% 6% 2 5% 3 3 5% 4 6% 8% 46%	1393
	11th to 20th	Night	12% 6% 2 5% 4 3 5% 5% 6% 10% 43%	1330
	21st to end	Night	8% 4 2 5% 3 4 5% 3 6% 8% 52%	1330
July	1st to 10th	Night	5% 3 2 4 3 4 5% 5% 7% 10% 53%	2220
	11th to 20th	Night	4 3 1 4 3 4 4 4 6% 8% 58%	2316
	21st to end	Night	2 3 1 3 3 3 4 3 7% 8% 64%	2761
August	1st to 10th	Night	8% 5% 1 4 3 2 3 3 6% 7% 58%	2528
	11th to 20th	Night	5% 2 2 4 3 3 4 3 7% 9% 58%	2646
	21st to end	Night	7% 3 1 3 4 3 4 4 5% 7% 57%	3358
September	1st to 10th	Night	9% 4 1 4 4 3 4 3 4 7% 56%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 3 3 5% 8% 50%	1900
	21st to end	Night	11% 4 1 5% 3 3 4 3 5% 7% 53%	2146
October	1st to 10th	Night	9% 6% 2 5% 3 3 4 3 5% 7% 54%	3800
	11th to 20th	Night	5% 5% 2 5% 3 3 3 3 5% 11% 54%	3778
	21st to end	Night	6% 8% 2 6% 4 4 5% 4 7% 8% 44%	4464
November	1st to 10th	Night	13% 14% 4 8% 5% 4 4 3 5% 6% 35%	2682
	11th to 20th	Night	7% 11% 4 12% 6% 5% 5% 4 6% 7% 34%	2800
	21st to end	Night	7% 13% 5% 11% 6% 5% 5% 4 5% 7% 34%	2800
December	1st to 10th	Night	7% 14% 6% 14% 8% 6% 5% 3 4 6% 26%	4724
	11th to 20th	Night	5% 13% 6% 14% 8% 7% 6% 4 5% 6% 25%	5557
	21st to end	Night	3 8% 4 10% 7% 4 4 3 5% 6% 46%	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	62% 5% 13% 16% 4	3179
	11th to 20th	Day	52% 7% 13% 17% 10%	3478
	21st to end	Day	43% 4 26% 23% 3	4004
February	1st to 10th	Day	59% 5% 9% 17% 10%	1734
	11th to 20th	Day	54% 5% 13% 14% 13% 1	1764
	21st to end	Day	51% 7% 15% 17% 9%	1575
March	1st to 10th	Day	50% 5% 18% 20% 6%	4500
	11th to 20th	Day	46% 8% 18% 24% 4	4908
	21st to end	Day	58% 6% 15% 14% 6%	5790
April	1st to 10th	Day	44% 7% 15% 22% 11% 1	2400
	11th to 20th	Day	53% 6% 14% 19% 6% 1	2379
	21st to end	Day	46% 6% 15% 23% 9% 1	2755
May	1st to 10th	Day	49% 6% 14% 22% 7% 1	4570
	11th to 20th	Day	39% 9% 15% 27% 11%	4394
	21st to end	Day	44% 9% 17% 23% 6%	4825
June	1st to 10th	Day	42% 7% 17% 24% 9% 1	2783
	11th to 20th	Day	47% 7% 15% 21% 10% 1	2850
	21st to end	Day	33% 7% 19% 32% 9% 1	2850
July	1st to 10th	Day	31% 6% 22% 25% 15% 1	4666
	11th to 20th	Day	21% 6% 16% 36% 19% 3	4552
	21st to end	Day	19% 4 9% 36% 24% 9%	4651
August	1st to 10th	Day	31% 4 14% 31% 19% 2	4396
	11th to 20th	Day	26% 4 18% 36% 15% 1	4232
	21st to end	Day	27% 3 12% 40% 16% 2	4308
September	1st to 10th	Day	33% 5% 14% 27% 17% 4	2280
	11th to 20th	Day	36% 5% 16% 27% 13% 3	2280
	21st to end	Day	36% 4 12% 29% 16% 2	2033
October	1st to 10th	Day	32% 3 11% 35% 16% 3	3170
	11th to 20th	Day	29% 3 14% 38% 13% 3	3121
	21st to end	Day	37% 4 16% 34% 9%	3091
November	1st to 10th	Day	49% 5% 14% 22% 9% 1	1613
	11th to 20th	Day	49% 6% 16% 21% 8% 1	1600
	21st to end	Day	51% 7% 20% 17% 4 1	1600
December	1st to 10th	Day	54% 6% 21% 14% 5%	2457
	11th to 20th	Day	60% 5% 22% 9% 4	2617
	21st to end	Day	40% 4 10% 28% 13% 5%	3498
January	1st to 10th	Night	54% 5% 17% 18% 6%	6766
	11th to 20th	Night	53% 5% 14% 16% 11% 1	6492
	21st to end	Night	45% 5% 23% 24% 3	6974
February	1st to 10th	Night	54% 6% 13% 17% 9% 1	2685
	11th to 20th	Night	50% 5% 15% 17% 11% 1	2533
	21st to end	Night	45% 5% 14% 25% 11%	2055
March	1st to 10th	Night	44% 6% 19% 20% 10%	5374
	11th to 20th	Night	44% 6% 18% 25% 7%	5073
	21st to end	Night	61% 5% 13% 15% 5%	5170
April	1st to 10th	Night	39% 6% 15% 26% 13% 1	2000
	11th to 20th	Night	48% 5% 12% 21% 12% 2	1969
	21st to end	Night	43% 6% 13% 25% 12%	1645
May	1st to 10th	Night	46% 8% 10% 25% 11% 1	2620
	11th to 20th	Night	36% 7% 14% 28% 14% 1	2522
	21st to end	Night	38% 10% 15% 30% 6%	2762
June	1st to 10th	Night	35% 6% 17% 27% 13% 2	1393
	11th to 20th	Night	35% 6% 18% 24% 14% 2	1330
	21st to end	Night	29% 8% 17% 33% 12% 1	1330
July	1st to 10th	Night	26% 6% 26% 29% 13% 1	2185
	11th to 20th	Night	23% 4 15% 30% 24% 3	2274
	21st to end	Night	17% 3 11% 39% 21% 8%	2674
August	1st to 10th	Night	26% 3 14% 35% 21% 1	2520
	11th to 20th	Night	23% 4 15% 39% 17% 1	2670
	21st to end	Night	26% 4 14% 35% 18% 3	3358
September	1st to 10th	Night	29% 4 11% 30% 20% 6%	1900
	11th to 20th	Night	32% 5% 13% 28% 18% 3	1900
	21st to end	Night	32% 4 12% 32% 18% 2	2146
October	1st to 10th	Night	31% 3 13% 31% 20% 2	3800
	11th to 20th	Night	26% 3 13% 42% 14% 1	3778
	21st to end	Night	37% 4 11% 36% 12% 1	4464
November	1st to 10th	Night	50% 5% 14% 21% 9% 2	2682
	11th to 20th	Night	49% 5% 18% 20% 7% 1	2800
	21st to end	Night	50% 5% 19% 20% 6%	2800
December	1st to 10th	Night	60% 4 18% 12% 4	4724
	11th to 20th	Night	60% 5% 18% 14% 3	5558
	21st to end	Night	40% 3 11% 26% 15% 4	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	11% 14% 32% 26% 14% 4	200
	11th to 20th	Day	11% 10% 35% 27% 13% 4	265
	21st to end	Day	12% 11% 36% 30% 9% 2	330
February	1st to 10th	Day	16% 9% 42% 25% 7% 1	300
	11th to 20th	Day	9% 9% 40% 27% 13% 2	300
	21st to end	Day	5% 10% 37% 31% 14% 2	249
March	1st to 10th	Day	12% 8% 36% 29% 12% 3	300
	11th to 20th	Day	11% 13% 34% 25% 12% 5%	460
	21st to end	Day	14% 9% 36% 25% 13% 4	550
April	1st to 10th	Day	11% 15% 39% 29% 6% 1	500
	11th to 20th	Day	18% 13% 34% 27% 6% 2	492
	21st to end	Day	19% 10% 27% 31% 12% 1	655
May	1st to 10th	Day	15% 7% 25% 31% 18% 5%	703
	11th to 20th	Day	14% 8% 24% 29% 19% 7%	676
	21st to end	Day	16% 8% 24% 26% 20% 6%	734
June	1st to 10th	Day	16% 12% 25% 27% 15% 5%	680
	11th to 20th	Day	17% 13% 32% 23% 12% 3	680
	21st to end	Day	11% 6% 26% 31% 20% 6%	680
July	1st to 10th	Day	6% 4 26% 34% 23% 6%	671
	11th to 20th	Day	6% 5% 26% 38% 20% 5%	668
	21st to end	Day	5% 5% 26% 32% 25% 6%	739
August	1st to 10th	Day	10% 4 22% 37% 21% 7%	676
	11th to 20th	Day	11% 4 23% 31% 23% 8%	577
	21st to end	Day	11% 6% 22% 36% 19% 6%	539
September	1st to 10th	Day	11% 8% 30% 30% 17% 5%	490
	11th to 20th	Day	14% 9% 27% 33% 14% 3	490
	21st to end	Day	16% 10% 27% 30% 12% 4	329
October	1st to 10th	Day	21% 6% 25% 25% 20% 2	300
	11th to 20th	Day	10% 11% 34% 28% 12% 4	300
	21st to end	Day	15% 11% 40% 25% 8% 2	330
November	1st to 10th	Day	19% 9% 37% 22% 11% 2	300
	11th to 20th	Day	13% 16% 35% 24% 11% 1	300
	21st to end	Day	11% 12% 37% 26% 12% 1	300
December	1st to 10th	Day	11% 11% 45% 23% 7% 2	300
	11th to 20th	Day	12% 14% 40% 23% 10% 1	260
	21st to end	Day	13% 6% 34% 33% 11% 3	220
January	1st to 10th	Night	8% 14% 40% 30% 9% 1	1000
	11th to 20th	Night	10% 13% 40% 29% 8% 1	1000
	21st to end	Night	12% 11% 40% 27% 8% 1	1100
February	1st to 10th	Night	11% 11% 33% 30% 13% 2	885
	11th to 20th	Night	11% 9% 39% 30% 9% 1	784
	21st to end	Night	8% 9% 31% 32% 16% 4	660
March	1st to 10th	Night	10% 9% 34% 34% 11% 2	800
	11th to 20th	Night	12% 9% 36% 33% 10% 2	800
	21st to end	Night	14% 7% 28% 37% 13% 1	742
April	1st to 10th	Night	10% 9% 32% 39% 10%	600
	11th to 20th	Night	15% 8% 37% 32% 7%	593
	21st to end	Night	17% 8% 30% 37% 9%	600
May	1st to 10th	Night	15% 5% 27% 38% 14% 1	600
	11th to 20th	Night	15% 6% 25% 35% 17% 2	563
	21st to end	Night	19% 8% 22% 32% 18% 1	617
June	1st to 10th	Night	13% 8% 29% 35% 14% 2	443
	11th to 20th	Night	16% 6% 27% 38% 13%	380
	21st to end	Night	12% 4 26% 39% 16% 2	380
July	1st to 10th	Night	8% 3 23% 45% 20% 1	370
	11th to 20th	Night	8% 3 28% 45% 16% 1	425
	21st to end	Night	3 4 29% 48% 16% 1	624
August	1st to 10th	Night	8% 3 23% 46% 17% 3	567
	11th to 20th	Night	6% 4 21% 45% 23% 2	564
	21st to end	Night	10% 3 25% 42% 19% 1	627
September	1st to 10th	Night	10% 4 25% 44% 16% 2	570
	11th to 20th	Night	10% 5% 24% 44% 16% 1	570
	21st to end	Night	12% 5% 30% 40% 12% 1	655
October	1st to 10th	Night	18% 7% 28% 34% 13% 1	760
	11th to 20th	Night	13% 6% 33% 34% 13% 2	760
	21st to end	Night	14% 9% 38% 31% 8%	1042
November	1st to 10th	Night	20% 9% 35% 29% 5% 1	975
	11th to 20th	Night	12% 11% 41% 26% 9% 1	1000
	21st to end	Night	12% 10% 45% 25% 7% 1	1000
December	1st to 10th	Night	13% 9% 38% 27% 11% 2	1000
	11th to 20th	Night	13% 12% 36% 29% 9% 1	1000
	21st to end	Night	12% 8% 36% 32% 10% 2	1100

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